Senior backend engineer
Summary
A ~6-month contract (Nov 2026 start, extension option) for a senior backend engineer working on-site in Stockholm on a core real-time product. Day to day: build and ship Node.js/TypeScript services with MongoDB and Redis, design event-driven microservices and low-latency audio/streaming pipelines, and keep observability, testing, and security up to standard.
Role: Senior backend engineer
Job Ref Id: JD-1262
Competence level: 5+ years
Start date: 2026-11-02
End date: 2027-04-30
Extension option: Yes
Scope: 100%
Location: Stockholm
Remote work: On-site
Language: English
Application deadline: 2026-10-25
Number of consultants: 1
Security clearance: No
About the assignment
We are looking for an experienced backend engineer with expertise in Node.js and MongoDB to work on one of our core products.
Responsibilities
- Develop and maintain Node.js applications
- Deploy and release new capabilities, features and fixes
- Ensure quality standards, including test automation, manage tech debt, etc.
- Collaborate with product managers to define the product roadmap
- Write and maintain tech documents, including RFCs, ADRs, postmortems, etc.
- Own tech roadmap and priorities aligning with product priorities
- Ensure observability and monitoring match industry standards
- Proactively address security issues in collaboration with our security department
- Join and actively contribute to team ceremonies
- Propose improvements in our SDLC
- Proactively identify cost saving opportunities
Requirements
Mandatory
Solid experience with TypeScript/JavaScript/Node.js and MongoDB (Mongoose ODM)
Experience with real-time/streaming systems design (e.g. WebSockets, low-latency audio pipelines, etc.)
Hands-on experience with Redis / ioredis (caching, rate limiting, pub/sub)
Experience with event-driven applications and messaging systems
Solid experience with microservices architecture and async programming
Experience with observability/metrics tooling (e.g. Prometheus, structured logging)
Nice-to-have
Experience with BullMQ and Node's Cluster module, working with workers and subprocesses
Experience with LLMs and audio processing (STT/TTS)
Experience with Keystone and Express.js
Experience with gRPC and Protocol Buffers
Experience with NATS (messaging queue)
Experience with Docker and Docker Compose
Experience with Kubernetes + ArgoCD + Kustomize (multi-region GKE deployments)
Experience with Go and WebSocket bridging services
Experience with cloud/VoIP telephony and telecom generally
Experience with Kamailio / Homer
Experience with Asterisk PBX / ARI (Asterisk REST Interface) and SIP/IAX protocols
Experience with Firebase Admin / APNs