Jobs Java

About Flamingo

Flamingo is revolutionizing the Managed Service Provider (MSP) industry with an AI-driven, open-source platform for IT and security. Our goal is to empower MSPs with automation, optimization, and scalability tools to enhance their operations. 

Role Overview

As a Senior Back-end Engineer (Java) at Flamingo, you will design and develop scalable, high-performance back-end services and APIs using Java and Spring Boot. You will be responsible for implementing event-driven microservices, optimizing system performance, and ensuring high availability as we scale our platform. Your expertise in processing high-volume logs and integrating multiple data sources will be critical to building a robust and efficient system.

Key Responsibilities

• Design and develop scalable backend services and APIs using Java (Spring Boot).
• Architect and implement event-driven microservices with Kafka and RabbitMQ.
• Process and analyze high-volume logs efficiently to ensure scalability and real-time insights.
• Integrate and manage multiple data sources, including SQL, NoSQL, and streaming data.
• Optimize database performance using PostgreSQL, Redis, and Elasticsearch.
• Implement authentication and authorization mechanisms with OAuth, JWT, and Keycloak.
• Collaborate with front-end and DevOps teams to build a seamless and resilient system.
• Ensure code quality through automated testing, CI/CD pipelines, and best engineering practices.

Qualifications

Must-Have:

• 5+ years of experience in backend development with Java and Spring Boot.
• Experience in microservices architecture, including event-driven systems (Kafka, RabbitMQ).
• Strong knowledge of RESTful APIs, GraphQL, and WebSockets.
• Experience processing high-volume logs and working with log management tools (ELK stack, Loki, Fluentd, OpenTelemetry).
• Experience working with multiple data sources, including relational (PostgreSQL) and non-relational (Redis, Elasticsearch) databases
• Experience with containerization (Docker, Kubernetes) and cloud platforms (AWS/GCP).
• Understanding of security best practices in backend development.

Nice-to-Have:

• Experience with functional programming in Java or Scala.
• Familiarity with distributed tracing (e.g., Jaeger, Zipkin) for microservices.
• Knowledge of cloud-native architectures and serverless frameworks.
• Exposure to message queues and event sourcing.

Why Join Flamingo?

• High-impact role: As a back-end engineer, your contributions will directly shape Flamingo’s product and technology.
• Ownership & Equity: Competitive compensation, including significant equity in an early-stage, high-growth startup.
• Innovative Tech Stack: Work with cutting-edge open-source technologies in AI, automation, and security.
• Remote-first Culture: Flexibility to work from anywhere while collaborating with a top-tier team.
• Mission-Driven Company: Join a team passionate about disrupting the MSP industry and making enterprise-grade security and IT automation accessible to all.

N-iX is looking for an experienced Senior Java Engineer who goes beyond standard CRUD APIs and lives in the world of information retrieval.

Our customer is a Fortune 500 company. As a leading business-to-business organization, more than 3.2 million customers rely on its products in categories such as safety, material handling, and metalworking, along with services like inventory management and technical support. ​

In this role, you will act as the bridge between our core Java application architecture and our specialized search infrastructure. You will be responsible for the entire search lifecycle: from designing how data is ingested and indexed, to building the Java APIs that query that data, and crucially, tuning the relevancy algorithms that ensure our users find exactly what they are looking for, instantly. The ideal candidate has deep roots in the Apache Solr ecosystem but is also ready to embrace modern cloud-native search via AWS OpenSearch. Whether you are maintaining critical legacy Solr clusters or architecting new solutions on AWS, your goal is to make data findable, fast, and relevant.

Technology stack: Java/Spring Boot, Apache Solr (Legacy/Core), AWS OpenSearch (Modern/Growth), SQL DB, Kafka 

Responsibilities:

• Design, develop, and maintain high-performance backend Java services (primarily Spring Boot) that integrate with search engines.
• Build complex search features for the frontend, including faceted navigation (filtering), multi-tenant searching, real-time autocomplete/typeahead, and spell-checking suggestions.
• Utilize Java client libraries (such as Solr or AWS SDKs) to construct efficient, programmatic queries.
• Take ownership of the search schema design, deciding how complex data structures should be analyzed, tokenized, and stored for optimal retrieval.
• Build robust ETL pipelines in Java (potentially using Kafka or other messaging systems) to synchronize data from primary SQL databases into the search indices in near real-time.
• Configure analyzers, stemmers, and tokenizers to handle nuances in human language.
• Diagnose slow queries, analyze search logs, and optimize both Java application code and search engine configurations for low-latency performance.
• Maintain and optimize existing on-premise or cloud-hosted Apache Solr installations.
• Play a key role in designing hybrid strategies or migration paths from legacy Solr systems to managed AWS OpenSearch environments.

Requirements: 

• 5+ years of professional experience in backend software development using modern Java (Java 8+, Spring Boot ecosystem).
• Strong, demonstrable experience with Search Technologies. This means either:
  • Hands-on production experience configuring, managing, and developing against Apache Solr (understanding schema.xml, solrconfig.xml, Zookeeper integration).
  • OR deep foundational knowledge of Lucene-based search concepts (inverted indices, analysis chains, TF-IDF/BM25 scoring logic) with the ability to quickly apply that to Solr.
• Hands-on experience with AWS OpenSearch (or Elasticsearch) in a managed cloud environment.
• Experience with data modeling in relational databases (PostgreSQL, MySQL, Oracle).
• Strong understanding of RESTful API design principles.
• Preferred Qualifications:
  • Experience architecting zero-downtime migrations from self-hosted Solr to managed cloud search services.
  • Experience with event-driven architecture and streaming tools like Apache Kafka for real-time indexing.
  • Familiarity with containerization (Docker, Kubernetes) and CI/CD pipelines like Jenkins or GitLab CI.

We offer*:

• Flexible working format - remote, office-based or flexible
• A competitive salary and good compensation package
• Personalized career growth
• Professional development tools (mentorship program, tech talks and trainings, centers of excellence, and more)
• Active tech communities with regular knowledge sharing
• Education reimbursement
• Memorable anniversary presents
• Corporate events and team buildings
• Other location-specific benefits

*not applicable for freelancers

This vacancy requires office attendance in Kyiv

Responsibilities

• Work in SCRUM team 
• Design and develop high-load microservices
• Write high-quality code covered with different levels of tests
• Maintain services on production and assure their stability and performance
• Provide code review for teammates 
• Contribute to the Company’s development processes and practices 

Requirements

• Writing code in a clean and maintainable manner.
• Solid experience with Java 8+ 
• Experience with SQL/NoSQL databases
• Understand microservice architecture patterns.
• Good at Spring framework.
• Experience with REST, messaging systems.
• Ability to cover code by different types of tests.
• Understanding of SOLID principles
• Experience with Git 
• Excellent troubleshooting skills.
• Good communication skills.
• Intermediate+ English

Would be great to have:

• Experience with Kafka, MySQL, Redis, Aerospike.
• Experience with Spring Boot, Spring Cloud
• Experience with Docker, Kubernetes
• Experience in high-load

What we offer:

• International company with several offices in different locations : Tel-Aviv, Kyiv, Warsaw, Limassol.
• Granting an Option;
• A professional environment with great people to work with;
• Competitive salary, performance review;
• Flexible working hours, no one here tracks your work time because our culture is built on trust and cooperation;
• Social and welfare packages;
• 20 working days paid vacation and 100% sick leaves coverage;
• Opportunities to make a difference, to develop and grow;
• Regular corporate celebrations, team buildings and fun activities;
• Comfortable office close to the metro station. Our Kyiv office is open 24/7 with all safety and health measures in place.

CrunchCode — міжнародна сервісна ІТ-компанія з досвідом близько 7 років у розробці вебсервісів і вебзастосунків. Ми працюємо у форматах staff augmentation (outstaff) та outsourcing і підключаємо спеціалістів до проєктів клієнтів у довгостроковій моделі співпраці.

Ми працюємо переважно з проєктами в доменах логістики (включно з last mile),e-commerce, fintech та банкінгу, а також enterprise-рішеннями.
Для нас важливо, щоб проєкт був “чистим” і зрозумілим з точки зору етики та цінності для користувачів.

Ми принципово не беремо проєкти, пов’язані з:
● gambling / гемблінгом,
● adult-контентом та порнографією,
● шахрайством або будь-якою розробкою, що спрямована на обман чи маніпуляції.

What We Offer:
● Fully remote work
● Long-term, stable project
● High level of autonomy and trust
● Minimal bureaucracy
● Direct impact on business-critical logistics systems
● Long-term engagement, not a short-term contract.

Project Overview: Senior-level backend role, ideally approaching Architect level, focused on designing and developing core backend services for ORA. The work enables secure cloud integration with SEF through KMIP and Barbican, requiring deep expertise in cryptography, Kubernetes, and open-source / open-standard solutions.

Tech Stack: Java · Kubernetes · OpenStack · KMIP · Barbican · TLS · CRDs · Distributed Systems

Requirements (Must-have):

• Extensive senior-level backend development experience in Java
• Crypto hands-on experience — must be clearly visible in CV
• Strong knowledge of cryptography — TLS and data encryption
• Practical Kubernetes experience — infrastructure and management layers
• Familiarity with OpenStack
• Experience writing unit and integration tests for backend systems
• Ability to design and work with complex distributed systems and core services
• Fluent English — C1 minimum
• Location: Europe (remote)
  
  Responsibilities:
• Design and develop ORA's core backend services, integrating with KMS via KMIP for components like Barbican and Ceph
• Build and manage Kubernetes-based infrastructure — CRDs, operators, and controllers
• Implement secure communication mechanisms using TLS and advanced encryption methods
• Work closely with architecture and infrastructure teams across management layers
• Create and maintain unit and integration tests for high-quality, reliable code
• Contribute to architectural decisions and provide technical leadership in backend development
  
  Nice to Have: 
  At least one of the following is strongly preferred:
• Knowledge of KMIP and secure key management practices
• Experience with Barbican and open-standards integrations
• Experience with cloud convergence concepts and ORA architecture
• Understanding of scalability and performance optimization in microservices
  
  Hiring Process: Intro call → Technical discussion → Offer

About Us

levl (www.levl.ch) offers a single unified platform for fast, secure, and cost-effective cross-border payments. Platforms can plug into our payments API, use our dashboard, or OTC desk to send and receive payments for their customers.

levl is incubated and funded by Galaxy Digital, a public financial services firm managing $5b+ AUM, and based out of their European offices. levl’s team previously worked at top payment companies, exchanges, and hedge funds including PayPal, London Stock Exchange, AQR ($150b+ quant fund), Brevan Howard, and Galaxy Digital.

About the Role

We are looking for a talented Backend Software Engineer to help build Levl’s payments platform. This is an opportunity to join a fast-paced early-stage startup in which you will be given tremendous ownership and autonomy.

You will play a pivotal role in leveraging stablecoins to democratize access to financial services and shape the future of financial inclusion. If you're passionate about Software Engineering, love building products, and want to transform the financial landscape, we want you on our team!

Key Responsibilities

• Working with cross-functional teams to build mission-critical financial services web products. You will be building microservices, API’s, web applications, and integrations to support cross-border payments and related back-office operations.

• Working closely with the CTO and contributing to ongoing efforts to enhance our payments platform.

   

Requirements

• Minimum 3 years of development of microservices
• Proficiency in Java or Golang and related frameworks, e.g. Spring Boot, Gin
• Proficiency with relational databases (ex PostgreSQL)
• Experience with Docker, Kubernetes, Helm etc
• Experience working with message buses such as NATS, Kafka
• Experience in building cloud-native services using AWS, GCP, or Azure
• Experience in REST API development
• AI-native - experienced in leveraging AI technologies to build software (Claude, Cursor etc)
• Strong grasp of unit testing principles and testing libraries
• Strong problem-solving and communication skills.
• Ability to work with others in a fast-paced environment.

• Ability to self-organise and deliver high-quality work.

   

Nice to Have

• Experience building payment or trading systems
• Experience working with AWS-specific cloud services such as SQS, S3, IAM
• Front-end development experience using JavaScript, TypeScript, React, Next.js

Additional Information

•  Background checks will be carried out

About Us
Peratera is a UK-based fintech company, founded in 2022 and authorised by the FCA as an Electronic Money Institution.

We are building a modern, all-in-one payment platform that enables businesses to manage global payments and financial operations seamlessly.

Our solution allows companies to open multi-currency accounts, send and receive payments worldwide, and manage cross-border transactions from a single platform.

Our mission is to simplify global finance and remove friction from international business operations.

Your Mission 

As a Senior Java Engineer, you will be a core contributor to our distributed financial platform - going beyond coding to actively shape architecture, drive engineering excellence, and help build systems that are scalable, observable, and regulation-ready. You will join at a stage where the platform is evolving fast and the right engineers will grow with it - toward Tech Lead or Staff Engineer roles.

Your Tech Environment

You will work in a modern, cloud-native stack with clear ownership and no legacy surprises:

• Backend: Java 17+, Spring Boot (Core, Security, Data, Cloud), REST APIs, event-driven services, Camunda
• Infrastructure: AWS (EKS, RDS, CloudWatch), Docker, Kubernetes, GitLab CI/CD
• Data & Messaging: PostgreSQL, AMQP / Kafka-style message brokers, event-driven architecture
• Observability: OpenSearch / ELK, Prometheus / Micrometer, OpenTelemetry (in progress)
• Integrations: Open Banking providers, banking partners, external payment systems

What You’ll Do 

• Design and develop high-load, distributed backend services for financial operations
• Work on core payment flows, callbacks, reconciliation, and transaction lifecycle management
• Participate in architecture discussions and contribute to system design decisions
• Implement observability across services - logging, metrics, and distributed tracing
• Improve system reliability, fault tolerance, and overall platform resilience
• Drive code quality, testing strategy, and engineering best practices across the team
• Collaborate closely with Product, DevOps, and Architecture teams
• Contribute to the platform's evolution toward AI-assisted and data-driven capabilities
   

What We’re Looking For

• 6+ years of strong, production Java experience
• Deep expertise in the Spring Boot ecosystem
• Solid understanding of distributed systems and microservices architecture
• Experience building high-load or financial systems - payments, banking, or fintech
• Strong REST API design skills and hands-on experience with messaging systems
• Solid SQL skills; PostgreSQL experience preferred
• Familiarity with cloud environments, CI/CD pipelines, and observability tooling
• Clean Code mindset - SOLID principles, maintainability, and genuine ownership
• Comfortable working asynchronously in a distributed, international team
   

Nice to Have

• Exposure to Open Banking or regulated payments environments
• Experience with Camunda or other workflow orchestration engines
• Understanding of PCI DSS compliance requirements
• Experience with event-driven or event-sourcing architectures
• Interest or hands-on experience with AI/ML applied to backend systems
   

What You’ll Get

• Competitive, market-aligned compensation - discussed openly at first interview
• Direct impact on architecture and strategic platform decisions from day one
• A real fintech platform running at production scale - not a demo environment
• Exposure to modern cloud-native, AI-assisted, and Open Banking systems
• Fully remote setup with flexible hours and an international, highly skilled team
   

Sounds like a match? Send us your CV - we’re excited to get to know you.

Senior Java Blockchain Engineer

Java + BTC + ETH + Solana + TRON

Full-time, EU timezone (±)

Location: Europe (preferred)

Project Overview

Building an internal wallet technology platform for custodial operations across Bitcoin, Ethereum, Solana, and TRON. The goal is to replace a fragmented setup of multiple vendor-specific tools with a unified, client-owned stack — consolidating policy engines, wallet registries, and governance frameworks into a single system.

Platform scope: policy and governance · wallet management · transaction construction and execution · signing coordination

Responsibilities

Design and develop a unified custodial wallet platform from the ground up

Build and maintain wallet management, transaction construction, and signing coordination modules

Implement policy and governance layers for multi-chain operations

Integrate blockchain protocols: Bitcoin, Ethereum, Solana, TRON

Ensure security, scalability, and reliability of the custody infrastructure

Consolidate existing vendor-specific tools into a single client-owned stack

Requirements (Must-have)

Strong hands-on Java development experience in production environments

Proven experience with blockchain protocols — BTC, ETH, Solana, TRON

Deep understanding of wallet infrastructure: key management, signing flows, transaction lifecycle

Experience building or integrating custodial / non-custodial wallet systems

Solid understanding of cryptographic primitives (signing schemes, key derivation)

EU timezone availability, full-time commitment

Nice to Have

Experience with HSM or MPC-based signing coordination

Familiarity with multi-chain wallet registries

Prior work on fintech or crypto custody platforms

Tech Stack

Java · Bitcoin · Ethereum · Solana · TRON · Wallet Infrastructure

Hiring Process

Intro call → Technical discussion → Offer

Start: ASAP

Duration: Long-term (8+ months)

About the Role

We're seeking an experienced Middle Java Developer to join our backend engineering team. You'll design and implement scalable server-side solutions, collaborate with cross-functional teams, and help shape our technical direction. This position offers the opportunity to work on mission-critical systems and develop your expertise toward a senior role.
 

Key Responsibilities

• Develop and maintain robust Java applications and microservices
• Design scalable backend solutions following SOLID principles and design patterns
• Collaborate with frontend, DevOps, and product teams to deliver features
• Conduct code reviews and mentor junior developers
• Optimize application performance, security, and reliability
• Participate in system architecture design and technical decisions
• Write clean, maintainable code with comprehensive testing
   

Required Skills

• 3-5 years of professional Java development experience
• Strong proficiency in Java 8+ (including streams, lambdas, and modern features)
• Experience with Spring Framework (Spring Boot, Spring MVC, Spring Data)
• Knowledge of relational databases (SQL) and ORM tools (Hibernate, JPA)
• Solid understanding of REST API design and HTTP protocols
• Experience with version control systems (Git)
• Familiarity with unit and integration testing (JUnit, Mockito, TestNG)
• Problem-solving skills and ability to write clean, maintainable code
   

Nice to have

• Experience with microservices architecture and distributed systems
• Knowledge of message brokers (RabbitMQ, Apache Kafka)
• Familiarity with Docker and container orchestration
• Experience with CI/CD pipelines and automation tools
• Understanding of cloud platforms (AWS, GCP, Azure)
• NoSQL database experience (MongoDB, Redis)
• Agile/Scrum methodology experience
   

What We Offer

• Competitive salary commensurate with experience
• Remote or hybrid work options
• Professional development and training budget
• Collaborative, innovative team environment
• Clear career advancement opportunities
• Comprehensive benefits package

UAPP team needs a Backend Developer 

Requirements:

• experience with Java or other backend languages;
• strong understanding of OOP principles and SOLID;
• experience with Spring Boot or similar backend frameworks (e.g. NestJS, Django, etc.);
• knowledge of SQL, NoSQL and ORM tools (JPA / Hibernate or equivalents);
• experience in developing REST APIs;
• basic knowledge of algorithms and data structures;
• strong ability to learn new technologies and adapt to a new tech stack.

We offer:

• career and professional growth;
• decent salary;
• interesting projects in a professional team;
• trainings, seminars, meetings and conferences at company expense;
• pleasant and friendly working atmosphere.

UAPP is an IT company, established in 2018. We provide a full range of software development services, websites and mobile applications. Consulting, design, development, implementation, support and marketing — we do everything to achieve our clients’ business goals.

Our company's key to success is a team of professionals and like-minded people with solid practical experience in the field of project implementation for businesses and their own projects.

We offer services that are designed to take a client’s business to a new level and do everything to provide quality, innovation and creativity using the latest technology solutions.

System Department робить пристрої розумними, перетворюючи їх на повноцінний IoT. Вони створили й розвивають OS Malevich (модульна RTOS для різних апаратних платформ) і хмарний сервіс Ajax Cloud (Java 20 / Kotlin, AWS, Akka, NATS, Kafka, Mongo, MySQL). Для керування, обслуговування та моніторингу системи користувачами, інсталяторами й інженерами охоронних компаній розроблені додатки для iOS (Objective-C, Swift), Android (Java, Kotlin), Windows/macOS (Python / C++, QT, QML)

Responsibilities:

Core Development

• Design and implement core backend services and data pipelines
• Write clean, readable, and maintainable code
• Develop services for the B2B product line

Architecture & Documentation

• Participate in designing and improving system architecture
• Document architectural decisions and operational processes to support reliable deployment and service operations

Quality Assurance

• Ensure proper test coverage (unit and integration tests)
• Optimize performance and cost efficiency within owned areas
• Follow and promote best practices in software design and development

Operations & Monitoring

• Set up and maintain alerting, dashboards, and runbooks for production services
• Debug production issues, analyze complex cases, and conduct investigations

Collaboration & Culture

• Work in an engineering culture focused on testing, Continuous Delivery, and DevOps
• Collaborate with team members and other engineering teams to deliver features aligned with business needs

Requirements:

Required Experience

• 3+ years of professional backend development in Java (enterprise environment)
• Hands-on experience with Kotlin
• Strong understanding and practical experience with Java Concurrency

Architecture & Design

• Understanding of SOA, microservices, and event-driven architecture
• Practical experience with AWS and cloud development principles
• Experience building scalable, high-availability systems

Technologies & Tools

Required:

• Experience with NoSQL databases
• Experience with message brokers
• Familiarity with enterprise-grade stack (messaging systems, in-memory storage, key-value databases)
• Docker and Kubernetes
• Git, Gradle, Jenkins

Nice to Have:

• Redis, Netty, Akka
• gRPC, Project Reactor
• NATS, Kafka
• MongoDB

Testing & Quality

• Strong knowledge of unit testing
• Understanding of automated testing practices

What You Will Get

• Opportunity to propose and implement your own ideas with a real impact on the product and production
• Work in a highly motivated team with a zero-bullshit culture
• Competitive salary
• Health insurance
• Corporate English classes
• Compensation for professional development and learning
• Opportunity to participate in beta testing of Ajax security systems — get early access to and test new devices before their official release

Tango is a successful, market leader, a live-streaming Platform with 450+ Million registered users, in an industry projected to reach $240 BILLION in the next couple of years. 

The B2C platform, based on the best-quality global video technology, allows millions of talented people around the world to create their own live content, engage with their fans, and monetize their talents.

Tango live stream was founded in 2018 and is powered by 500+ global employees operating in a culture of growth, learning, and success!

The Tango team is a vigorous cocktail of hard workers, creative brains, energizers, geeks, overachievers, athletes, and more. We push the limits to bring our app from “one of the top” to “the leader”. 

The best way to describe Tango's work style is not to use the word “impossible”. We believe that success is a thorny path that runs on sleepless nights, corporate parties, tough releases, and of course our users' smiles (and as we are a LIVE app, we truly get to see our users all around the world smiling right in front of us in real-time!). 
 

Responsibilities

• Work in SCRUM team 
• Design and develop high-load microservices
• Write high-quality code covered with different levels of tests
• Maintain services on production and assure their stability and performance
• Provide code review for teammates 
• Contribute to the Company’s development processes and practices 
   

Requirements

• Writing code in a clean and maintainable manner.
• Solid experience with Java 8+ 
• Experience with SQL/NoSQL databases
• Understand microservice architecture patterns.
• Good at Spring framework.
• Experience with REST, messaging systems.
• Ability to cover code by different types of tests.
• Understanding of SOLID principles
• Experience with Git 
• Excellent troubleshooting skills.
• Good communication skills.
• Intermediate+ English
   

Would be great to have:

• Experience with Kafka, MySQL, Redis, Aerospike.
• Experience with Spring Boot, Spring Cloud
• Experience with Docker, Kubernetes
• Experience in high-load
   

What we offer:

• International company with several offices in different locations : Tel-Aviv, Kyiv, Warsaw, Limassol.
• Granting an Option;
• A professional environment with great people to work with;
• Competitive salary, performance review;
• Flexible working hours, no one here tracks your work time because our culture is built on trust and cooperation;
• Social and welfare packages;
• 20 working days paid vacation and 100% sick leaves coverage;
• Opportunities to make a difference, to develop and grow;
• Regular corporate celebrations, team buildings and fun activities;
• Comfortable office close to the metro station. Our Kyiv office is open 24/7 with all safety and health measures in place.

Tenexti is an emerging software development company based in Lviv. We specialize in creating innovative solutions, delivering high-quality results, and helping our clients turn their ideas into reality. With a passion for technology and a commitment to excellence, we strive to build lasting partnerships and drive meaningful impact through our work.

We are looking for a Java/Kotlin Developer to join our team.

🧑‍💻 What we expect from the ideal candidate:

• You have 1-3 years of experience working with Java in production environments.
   
• You are a good engineer. You don’t write code just to the point when it starts working. You go the extra mile to make your code elegant. You are passionate about technology and you take ownership of the things you implement. You have skills to design solutions that are simple, robust and easy to maintain.
   
• You are open-minded and eager to learn. Strong Java proficiency is required, but you should be comfortable working with Kotlin and functional programming patterns. We’re actively modernizing our codebase—new features are primarily written in Kotlin. You don’t need to be a Kotlin expert from day one, but you should be excited to grow in that direction.
   
• You think beyond just coding. Building great software isn’t about closing tickets—it’s about making the product and codebase better every time you touch it. You’re creative, you ask questions, and you care about the “why” behind what you’re building.
   
• You are a good team player. You treat people around you well and have strong communication skills to articulate technical decisions clearly.
   
• You don’t need supervision. You are self-driven and can solve problems on your own. You take initiative when you see opportunities for improvement.

💡 What you will do:

• Work on a mission-critical system that handles complex data synchronization workflows. System stability is paramount—downtime during peak hours leads to significant financial impact.
• Balance legacy and modern code. Help modernize existing Java code while building new features in Kotlin. Refactor legacy code, prune dead code, and gradually improve architecture while keeping the system stable.
• Implement complex business logic using sophisticated rules engines (like GoRules) for pricing logic, data mapping decisions, and business-critical workflows. You’ll participate in market analysis and some business decisions around pricing strategies.
• Optimize performance at scale. Process hundreds of thousands of records with strict rate limits. Identify bottlenecks, optimize database queries, improve API performance, and ensure queues don’t stack up.
• Participate in analytical decisions. While you’re a developer first, you’ll be involved in market analysis, system auditing, and even some business decisions around pricing and data strategies. We value engineers who understand the business impact of their work.
• Monitor system health extensively. Work with Grafana dashboards tracking dozens of critical metrics. Slowing of DB or API calls can cascade into serious issues.
• Perform code reviews. Suggest better, cleaner, and simpler approaches. Help the team grow by sharing knowledge.

Team and Customer:
We are a team of engineers based in Lviv working for a US-based customer. All engineers and architectural decisions are here locally—no late calls with the US, no overseas knowledge holders blocking you.
Our customer is not backed by venture capital but by reliable business revenue. We’re self-funded and don’t experience pressure to cut roles in Ukraine due to "country risks"—quite common lately.
We’re hiring due to business growth. By leveraging technology and smart people, we empower the business to grow further.

Product:
We work on a high-stakes data synchronization system handling hundreds of thousands of records in real-time. The product ensures data consistency between multiple systems while operating under strict rate limits and performance constraints.
This is a fascinating technical challenge—not a simple CRUD application, but a complex, performance-sensitive system where every optimization matters, stability is non-negotiable, and creative problem-solving is daily routine.

Technical highlights:

• Java monorepo with two main applications: a large-scale sales service (40GB RAM, 99.9%+ uptime) and a smaller purchase service. While development focus varies, you’ll need to be flexible across both
• Complex distributed architecture: Our Java apps depend on multiple Node.js microservices that serve as data providers. These Node apps are split across AWS and Hetzner, communicating via RabbitMQ
• Separate Redis instances for Java app and Node.js services
• Processes hundreds of thousands of records while respecting strict API rate limits (~700 requests/minute). Mistakes can take hours or days to fix
• Heavy reliance on Grafana dashboards with dozens of charts. Performance monitoring is critical—slowdowns cascade through the entire data pipeline

🚀 Our technology stack:
Backend:

• Java 21 & Kotlin (actively migrating towards more Kotlin)
• Spring Boot
• MongoDb, Redis
• GoRules for complex business logic

Infrastructure & DevOps:

• Kubernetes
• ArgoCD and Github Actions
• OpenSearch for logs
• Prometheus & Grafana for metrics & traces

The broader ecosystem:

• TypeScript, Node.js & Nest.js microservices
• PostgreSQL, Hasura & GraphQL

Projects you may work on:

• Modernizing the codebase: Refactoring legacy Java to Kotlin, improving architecture and maintainability
• Large-scale data migrations: Complex migrations with massive data volumes, zero downtime
• Performance optimization: Hunting tricky bottlenecks, optimizing queries, improving API response times
• Analytics improvements: Building features for transparent sales data and system metrics
• Business logic enhancements: Implementing clever mechanics using GoRules for pricing and data mapping
• System reliability: Enhancing monitoring, alerting, and recovery mechanisms

Why choose this project and team?

• Stable project running successfully for 8+ years with consistent revenue growth
• Entire R&D team in Ukraine making all architectural decisions locally
• Mission-critical production system where your decisions directly impact business outcomes
• Real engineering challenges: Performance optimization, rate limiting, data consistency, large-scale refactoring
• Opportunity to work on a quite high load production system (Monolith + microservices) and have an impact on how it is designed and shaped.

Perks and Benefits:

🏋️‍♂️ Gym compensation

🏝18 days of paid vacation, public holidays, and paid sick leave

💻 Modern tech gear: MacBook based on silicon CPU (M1-M3) with 32 of RAM

🇬🇧 English lessons

⏱️ Flexible working hours and no time trackers

✈️ Possible trips to USA when the war ends. Before the war, we flew there twice and we loved it :)

If you read this far please start your message with “Glory to Ukraine!”, thank you!

Looking for a Middle/Middle Strong Fullstack Java Developer to join our team. We are building a platform for fast and convenient purchase of tickets for various music and sport events. Users are provided access to a wide selection of concerts where they can find performances by their favorite artists, review event dates and locations, and buy tickets in real-time.

Requirements:

• 3+ years of experience in Java development.
• 2+ years of Spring framework and building Spring web applications.
• Understanding and experience developing and deploying microservices.
• Experience developing integration layers (using REST interfaces, OpenApi, Kafka, GraphQL).
• Commercial experience with frontend development (e.g., React, Angular, or similar frameworks).
• Excellent design, coding, and debugging skills.
• OOP, OOD, Design Patterns proficient.
• Knowledge of relational databases (preferably PostgreSQL).
• Experience with Docker.
• English — at least an Upper-Intermediate level.

Nice to have skills:

• Knowledge of non-relational databases.
• Experience in developing multi-threaded applications.
• Experience with AWS services (ECS, Lambda, Aurora).

Responsibilities:

• Produce code using Java best practices.
• Write unit tests and code that adheres to coding standards.
• Provide technical support.
• Work both independently and in close collaboration with others in the team; effectively communicate with geographically distributed team members.
• Make recommendations for the improvement of the system and development process to increase productivity.
• Identify, monitor, and resolve project-related issues.

Interview stages:

• HR-interview (30 minutes).
• Technical interview (1 hour).
• Interview with the customer (1 hour).
• Job offer🎉🎉🎉

We offer:

• Competitive salary + bonuses.
• Challenging tasks and projects.
• Personal growth.
• Flexible working hours.
• New hardware.
• Free English lessons.
• Availability of generators and Starlinks in the office.
• Small gym and table tennis in the office.
• Adjustable height tables.
• Regular office fruit delivery and other benefits.

Let’s create value together!

About Us: InnovatelU is a dynamic tech company delivering cutting-edge solutions. We're looking for a passionate Java Developer to join our team. If you have a solid Java foundation, are eager to grow, and learn quickly, we want to hear from you! 

Requirements: 
- Strong knowledge of Java 
- Knowledge of Spring (Spring Core, Spring AOP, Spring MVC, Spring Security, Spring Boot) 
- Familiarity with REST APIs, web services 
- Proficiency in version control tools (Git) 
- Experience with build tools like Maven and Gradle 
- Experience with relational databases (PostgreSQL) 
- Expertise in containerization (Docker) 

- Experience in unit and integration testing 
- Strong communication skills and teamwork ability 
- English level: Intermediate or higher 

Will Be a Plus: 

- Solid understanding of design patterns 

- Experience with NoSQL databases like MongoDB and Redis 

- Familiarity with messaging systems like Kafka and RabbitMQ 

- Experience with microservices architecture 

Responsibilities: 

- Collaborate with senior developers and project managers 

- Assist in designing, coding, and testing applications 

- Write well-designed, efficient, and testable code 

- Participate in code reviews 

- Debug and resolve technical issues 

- Contribute to application documentation 

Interview Stages: 

1. Test Task: 1 hour 

2. HR Interview: 30 minutes 

3. Technical Interview: 1 hour 

We Offer: 

- Full Remote 

- Constant support and mentoring 

- Paid 5 working days of sickness per a year; 

- Paid all official Ukrainian holidays; 

- 18 working days of vacation per a year; 

- Opportunity for professional growth and career development 

If this sounds interesting to you, let's talk!

Onicore is a FinTech company specializing in developing products for cryptocurrency operations. We strive to make crypto convenient and understandable for everyone.
 
And now we are looking for a talented and experienced Java Team Lead to join our team. If you’re passionate about working with the latest technologies, contributing to exciting product developments, and collaborating with an awesome team, we want to hear from you!
 
Your Key Duties:

• Design, develop, and maintain high-performance, scalable Java-based applications in the FinTech domain.
• Implement and optimize multithreaded and concurrent solutions, ensuring thread safety and system reliability.
• Build and maintain microservices using the Spring ecosystem.
• Ensure database efficiency, including query optimization, proper indexing, and transaction handling.
• Evaluate and improve application performance, conduct profiling sessions, and resolve bottlenecks.
• Design and implement synchronous and asynchronous integrations with internal and external systems.
• Participate in architectural discussions, propose improvements, and drive technical initiatives.
• Collaborate closely with product managers, architects, and QA engineers to deliver business-critical solutions.
• Write clean, maintainable, and well-tested code following best practices.
   

Your Skills:

• 5+ years of professional experience in Java development.
• Strong expertise in Java 17+ (knowledge of modern language features, streams, lambdas, functional programming concepts).
• Deep understanding of core Java:
• Collections Framework, Generics, Streams, Functional Interfaces
• Concurrency utilities (Executors, CompletableFuture, Fork/Join, Locks, Atomics, etc.)
• Proven experience with the Spring ecosystem: Spring Boot, Spring Data (JPA/Hibernate), Spring Security, Spring Cloud (microservices).
• Solid understanding of databases (SQL and/or NoSQL), including:
• Transactions, isolation levels, and locking mechanisms
• Query optimization and indexing strategies
• Hands-on experience with multithreading and concurrency, including race conditions, deadlocks, synchronization, and strategies to avoid them.
• Proficiency in synchronous and asynchronous communication: REST, messaging systems (Kafka, RabbitMQ, etc.), event-driven architectures.
• Experience working on FinTech or financial services projects.
• Strong focus on performance evaluation, scalability, and reliability.
• Strong problem-solving skills, ability to work independently, take initiative, and drive solutions proactively.
• Self-driven and responsible, capable of working with minimal supervision.
• Proactive, solution-oriented mindset.
• Team player with a collaborative attitude.
   

Nice to have:

• Experience with Kubernetes, Docker, and cloud-native environments.
• Experience with application profiling and performance tuning:
• Tools such as VisualVM, JFR (Java Flight Recorder), JMC (Java Mission Control)
• Identifying and resolving performance bottlenecks
• Analyzing complexity of SQL queries and optimizing execution plans
• Familiarity with CI/CD pipelines and DevOps practices.
• Knowledge of distributed systems, event sourcing, or CQRS.
   

What’s on us:

— Competitive salary and benefits package.

— Opportunities for professional development and career growth.

— Health insurance.

— Remote work with the possibility to visit our office in Kyiv.

— Space to share your ideas and bring them to life.

Is this all about you? Send us your CV!