Software Engineer – Database Kernel

Location: London 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. Intelligence that works. Results that matter. Built to work everywhere and integrate with everything across every cloud for dynamic, personalized, and autonomous AI systems. We deliver quicker results, contextual knowledge, and solutions that impact customers and employees across the business. 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. We are a pragmatic, engineering-led group split between Malmö and London. We read and discuss database papers (VLDB, SIGMOD, and others) to see what ideas are worth pulling into the product. We also run regular “Do What You Want” weeks so everyone has dedicated time to experiment with their own prototypes or tooling improvements. 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. Below are just a few exciting facts about Neo4j. Neo4j is one of the fastest-scaling technology companies in this industry. It recently surpassed $200M in annual recurring revenue (ARR), doubling its ARR over the past three years. Raised the biggest funding round in database history ($325M Series F). Backed by world-class investors like Eurazeo, GV (formerly Google Ventures), and Inovia Capital, Neo4j has raised over $600M in funding and is currently valued at over $2Bn. This puts Neo4j among the most well-funded database companies in history. 84% of the Fortune 100 and 58% of the Fortune 500 use Neo4j. Examples include Boston Scientific , BT Group , Caterpillar , Cisco , Comcast , Department for Education UK , eBay , NBC News , Novo Nordisk , Worldline , and others . Co-founder and CEO Emil Eifrem has built an amazing culture that prides itself on relationships, inclusiveness, innovation, and customer success. Countless industry awards . Massive enterprises and individual developers/data scientists love Neo4j. A strong sense of community and ecosystem is built around the platform. A recent Forrester Total Economic Impact™ Study cited Neo4j as delivering 417% ROI to customers. Research shows that members of underrepresented communities are less likely to apply for jobs when they don’t meet all the qualifications. If this is part of the reason you hesitate to apply, we’d encourage you to reconsider and give us the opportunity to review your application. At Neo4j, we are 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. We look forward to receiving your application. 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. We hire candidates who reflect the following Neo4j core values: (we)-[:VALUE]->(relationships) (we)-[:FOCUS_ON]->(userSuccess) (we)-[:THRIVE_IN]->(:Culture {type: [‘Open’, ‘Inclusive’]}) (we)-[:ASSUME]->(:Intent {direction:’Positive’}) (we)-[:WELCOME]->(:Discussions {nature: ‘IntellectuallyHonest’}) (we)-[:DELIVER_ON]->(ourCommitments) Neo4j is committed to protecting and respecting your privacy. Please read the privacy notice regarding Neo4j's recruitment process to understand how we will handle the personal data that you provide. More information at www.neo4j.com . ©2026 Neo4j, Inc., Neo Technology®, Neo4j®, Cypher®, Neo4j Bloom™, Neo4j Graph Data Science Library™, Neo4j® Aura™, and Neo4j® AuraDB™ are registered trademarks or a trademark of Neo4j, Inc. All other marks are owned by their respective companies.