Senior Backend Software Engineer

Own the backbone of a platform processing tens of thousands of messages per second, with no room for downtime.

Senior Backend Engineer - Real-Time Distributed Systems

Paris, France · Permanent · On-site

What you'd actually work on

• Designing and building highly available backend services for a real-time transactional platform
• Developing scalable microservices using server-side JavaScript and Node.js
• Building APIs and data models used across the wider platform
• Designing event-driven workflows for authentication, flow control, routing, and asynchronous messaging
• Improving application performance, concurrency handling, and resource usage
• Designing caching strategies while managing consistency and invalidation constraints
• Optimising relational database queries, indexes, transactions, and locking behaviour
• Building automated tests covering functional behaviour, integration, performance, and failure scenarios
• Running load and stress tests based on real production traffic patterns
• Deploying containerised services through automated CI/CD pipelines
• Implementing monitoring, logging, tracing, and alerting for production services
• Investigating incidents across application code, databases, messaging systems, and infrastructure
• Evolving critical services without interrupting a live platform used by hundreds of thousands of active users

Where it gets technically interesting

• Tens of thousands of messages processed every second through a gateway responsible for authentication, routing, and asynchronous messaging
• Event-driven architecture where retries, duplicate messages, ordering, and partial failures must be handled explicitly
• Node.js used for concurrent, high-throughput services beyond standard web applications
• Relational database performance under concurrent transactional workloads
• Query optimisation, transaction boundaries, and lock management under contention
• Caching decisions that directly affect performance, consistency, and availability
• Traffic spikes that must be absorbed without degrading the user experience
• Production changes requiring controlled rollout, monitoring, and rollback strategies
• Strict requirements around service availability and the protection of transactional and user data

What we're looking for

• 5+ years of experience building and operating backend services in production
• Strong experience with JavaScript or TypeScript and Node.js
• Experience designing microservices and event-driven systems
• Good understanding of distributed system failure modes
• Experience building services that handle high request or message volumes
• Strong knowledge of relational databases, data modelling, indexing, and query optimisation
• Understanding of transactions, locking, concurrency, and data consistency
• Experience designing and operating caching layers
• Practical knowledge of containers, CI/CD, and cloud infrastructure
• Experience with monitoring, logging, tracing, and production incident investigation
• Ability to evaluate performance, availability, and maintainability trade-offs
• Experience using Git, code reviews, and automated testing

The company

A fast-growing digital entertainment and online gaming company operating across several European markets.

The company employs several hundred engineers and generates revenue in the hundreds of millions of euros. Its transactional platform supports high traffic volumes and a large active user base, making availability, performance, and data security central engineering concerns.

Health insurance, profit-sharing, and an employee incentive scheme.

Languages: Native or bilingual French and professional English.

A search run by The French Sourcer, recruitment built for technical teams.