4GOO Holding GmbH

Senior Backend Engineer โ€” Golang / Distributed Systems

$$$

We're building a social networking platform from the ground up โ€” feed, posts, reels, stories, comments, reactions, chats, calls, livestreams, marketplace. We're looking for backend engineers to take ownership of significant parts of the system.

 

What you'll work on

Concrete things on the next 12 months of the roadmap:

- Feed generation, distribution, and the recommendation engine across posts, reels, stories, comments, and reactions: fan-out-on-write vs fan-out-on-read tradeoffs per content type, candidate generation, ranking pipeline (recency, affinity, engagement signals, content-type mixing), cold start, low-latency serving under heavy read load.
- A polymorphic engagement service (likes, comments, mentions, hashtags) across six content types, feeding engagement signals into the ranking pipeline.
- A real-time chat layer: WebSocket gateway with multi-device fan-out, Redis pub/sub event routing, presence and typing indicators.
- Audio/video calls: WebRTC signaling reusing our WS infrastructure, TURN/STUN, peer-to-peer media transport with SFU upgrade path.
- A marketplace service with Stripe Connect (escrow, separate charges, payout scheduling, KYC).
- Livestreams: RTMP ingest, HLS delivery, burst push notifications to follower bases of 100K+, integration with our chat infrastructure.
- CDC pipelines feeding OpenSearch for full-text and geo-search.

 

The stack

- Language: Go.
- Storage: PostgreSQL (relational), Cassandra/Amazon Keyspaces (high-write event logs), Redis (cache, pub/sub, ephemeral state), ClickHouse (analytics), OpenSearch (search).
- Platform: AWS EKS, all services as containers, API gateway.
- Observability: OpenTelemetry โ†’ Grafana OSS stack (Loki, Tempo, Mimir) for logs, traces, metrics, and alerting.
- Async: WebSocket, Redis pub/sub, FCM/APNS for push.
- Workflow: Product writes BRDs โ†’ we design the OpenAPI/AsyncAPI spec โ†’ backend ships a mock service โ†’ all teams develop in parallel โ†’ swap to real โ†’ QA โ†’ release. AI-assisted coding is part of how we work, not a side experiment.

 

What we're looking for

- Strong system design instincts. You can read a BRD, sketch the service boundaries, choose the right storage for each access pattern, and explain the tradeoffs. We care about this more than any specific framework.
- No tool tribalism. You pick the simplest thing that solves the problem. You don't reach for Kafka when Redis pub/sub does the job, and you don't reach for Postgres when the workload is append-only events.
- Production Go experience building backend services that are actually live somewhere, and comfort with concurrency primitives.
- Hands-on with at least most of: PostgreSQL, Redis, a wide-column store (Cassandra/Scylla/DynamoDB), an API gateway, containerized deployments on Kubernetes, OpenTelemetry-style observability.
- Independent operator. You don't wait to be told what to do next. You read the spec, identify the unknowns, ask the right questions early, and ship.

 

Bonus

- Feed, timeline, or recommendation systems experience โ€” fan-out architectures, candidate generation, ranking pipelines, ML-served scores in a serving path.
- Real-time systems experience (WebSocket gateways, presence, pub/sub fan-out).
- WebRTC or media-server work.
- Marketplace or payments work (Stripe Connect especially).
- Search infrastructure (OpenSearch / Elasticsearch, CDC pipelines).
- Terraform and infra-as-code comfort.

 

How we work

Small team, flat structure. Two-week sprints. Backend engineers own their services end-to-end: design, build, observe in production, fix. Engineers are expected to read specs, identify unknowns, ask questions early, and ship without being assigned next steps.

Required languages

English B1 - Intermediate
Ukrainian B1 - Intermediate
Go, PostgreSQL, Redis, Cassandra, AWS EKS
Published 26 May
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