Software Engineer – Database Kernel in Whitehall

About Neo4j: Neo4j is the graph intelligence platform that transforms data into knowledge to power the next generation of intelligent applications and AI systems. It includes enterprise-ready knowledge graphs for accurate, explainable, and governed AI; the most comprehensive, trusted, and easy-to-deploy graph capabilities across any environment and data source; and an unmatched ecosystem trusted by 84 of the Fortune 100 and supported by the world’s largest graph community.

Our Vision: At Neo4j, we have always strived to help the world make sense of data. As business, society and knowledge become increasingly connected, our technology promotes innovation by helping organizations to find and understand data relationships. We created, drive and lead the graph database category, and we’re disrupting how organizations leverage their data to innovate and stay competitive.

The Role: The Kernel team builds the storage engine and transaction machinery inside Neo4j. If you join us, you will not be building web APIs or shuffling data between services. Instead, you will be working directly on the database engine itself. Our day-to-day is low-level systems engineering. We write and maintain custom storage engines, the page cache, transaction handling (WAL, ACID guarantees), indexing, and memory management. The code we write determines how fast queries run across billions of nodes and relationships, and how safely data is written when a machine crashes.

What you will actually be doing:

• Designing, profiling, and implementing core database features, including storage formats, index structures, and recovery paths.
• Diagnosing tricky concurrency bugs, race conditions, and lock contention.
• Performance engineering: profiling CPU, memory allocation, off-heap memory, and disk I/O to improve latency.
• Reviewing designs and PRs with a heavy focus on correctness, data integrity, and long-term maintainability.
• Helping decide technical direction and architectural trade-offs as our engine evolves.

What we are looking for:

• Systems programming experience: You are comfortable working close to the hardware. Most of our codebase is Java, but if your background is in C++, Rust, or Go and you understand memory layouts and concurrency, that translates well.
• Concurrency and data structures: You have a clear understanding of threads, locks, atomic operations, cache locality, and algorithmic complexity.
• Pragmatic engineering: You write thorough tests because edge cases in database kernels are painful to debug in production.
• Collaborative attitude: You are comfortable having your technical choices questioned, you back up decisions with data or benchmarks, and you treat code review as a two-way discussion rather than a hurdle.

It is a bonus if you have:

• Prior experience with database internals, storage engines, or file systems.
• Deep knowledge of JVM internals, such as GC behavior, JIT compilation, and off-heap memory.
• Hands-on experience with profiling tools like async-profiler, JFR, or perf.
• Experience navigating and evolving large, mature codebases.

Why Join Neo4j? Neo4j is, without question, the most popular graph intelligence platform in the world. We have customers in every industry globally, and our products are a proven product/market fit. Joining our team is an opportunity to shape the future of data and analytics.

Neo4j is committed to building awareness and helping to improve these issues. One of our central objectives is to provide an inclusive, diverse, and equitable workplace for everyone to develop their potential and have a positive, career-defining experience.

Neo4j Values: Neo4j is a Silicon Valley company with a Swedish soul. We foster collaboration and each of us is empowered to contribute and put our innovative stamp on projects.