Senior Block-Builder Engineer

Adaptiq, on behalf of Eureka Labs, is looking for a Senior Block-Builder Engineer

About the Eureka Labs:

Eureka Labs runs a next-generation Ethereum block builder that operates live on mainnet across multiple regions, processing high volumes of DeFi transactions and competing in sub-millisecond latency auctions. It augments Ethereum’s capabilities, unlocks new DeFi primitives like intrablock lending, and enforces neutral, verifiable block construction via trusted execution. 

About the Role:

As a Senior Block-Builder Engineer at Eureka, you will own a production-grade, low-latency block-building platform and the systems that extend it: the seal-and-submit critical path, block-construction and bidding algorithms, parallel simulation, secure builder↔relay communication, and the off-chain logic that connects to a new on-chain lending protocol and a trust-minimized (TEE-based) execution model. You’ll turn open-ended problems – “how do we decide and bid faster than the competition,” “how do we let capital be borrowed and repaid safely inside one block,” “how do we prove we behaved honestly without exposing our edge” – into shipped, measurable systems.

Key Responsibilities:

• Optimize and drive down latency on the seal-and-submit path, identifying and removing bottlenecks in hot-path scans, allocations, state-root computation, and redundant clones.
• Transition block-construction and bidding logic from fixed heuristics to data-driven optimization models for transaction ordering and resource allocation.
• Build and maintain high-throughput parallel simulation (revm-based) to rank bundles per slot and integrate timing-correct PBS/MEV-Boost relay communication across regions.
• Design and implement an intrablock-lending protocol, coordinating off-chain builder logic with on-chain smart contracts and ensuring economic soundness.
• Integrate trusted execution environments (TEEs) or secure enclaves to enable verifiable, privacy-preserving execution of builder strategies.
• Contribute to the architecture of the execution-extension layer (BEX) and its integration with lending and simulation components.
• Establish safe deployment practices, deterministic simulation for rollback scenarios, and comprehensive observability for a financial-critical system.
• Maintain production reliability and participate in on-call rotation for immediate issue resolution in low-latency, high-stakes environments.

Required Competence and Skills:

• At least 7 years in backend software engineering focused on performance-critical systems handling real-time data and monetary transactions (e.g., trading, HFT, exchanges, low-latency networking).
• Typically 4+ years of blockchain experience, with the Ethereum ecosystem and deep understanding of the Ethereum protocol, node/client internals, and off-chain protocols.
• Production Rust experience, including async programming, concurrency, profiling, and allocation/contention tuning. Strong C++ or Go engineers with a credible and fast path to becoming productive in Rust will also be considered.
• Demonstrated low-latency experience: you can describe a real system you made meaningfully faster, how you identified the bottleneck, what you changed, and how you measured and proved the improvement.
• Strong analytical judgment: designing experiments, validating metrics against ground truth, and iterating based on data accuracy.
• End-to-end ownership of production systems and changes, including clear reasoning about architecture, blast radius, failure modes, safe rollouts, and rollback strategies.
• Ability to reason about correctness and economics simultaneously, ensuring protocol soundness without exploitable vectors.
• Fluent English communication skills and willingness to work within Eureka Labs’ hybrid office-first model in Poland.

Nice to Have:

• Working knowledge of PBS/MEV-Boost, block-builder relay timing games, and Ethereum consensus/execution internals (slots, epochs, fork choice, payload delivery).
• Experience contributing to core clients (reth, geth) or revm-based virtual machine projects.
• Exposure to trusted execution environments, secure enclaves, or applied cryptography.
• Smart-contract or on-chain protocol design experience.
• Background in optimization, operations research, or quantitative problem-solving.
• Prior contributions to MEV infrastructure, such as Flashbots or MEV-Boost.