Software Engineer – Database Kernel

About the role

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.