Senior Engineer

Our client
is one of Europe's fastest-growing mobile companies with 5 million active customers, 1,000 employees worldwide, and operations in five countries. The client is using the mobile virtual network operator business model.

We are looking for a
Senior Backend
result-oriented developer who has good knowledge and experience of

Responsibilities:

• Own microservices in NestJS (TypeScript):
  define module boundaries, version APIs, and ship resilient, well-tested services.
• Design internal communication:
  implement REST/gRPC/event-driven patterns (e.g., request/response, pub/sub), handle retries, timeouts, backoff, and circuit breakers.
• Implement secure JWT auth:
  access/refresh lifecycles, rotation, audience/issuer validation, revocation/blacklisting, and token storage best practices.
• Deliver payment integrations:
  integrate with gateways (e.g., Stripe/Adyen/Braintree), implement idempotent operations, handle captures/refunds/disputes, and reconcile via signed webhooks.
• Build and consume webhooks:
  define payload contracts, verify signatures/HMAC, ensure idempotency, and implement robust retry and DLQ strategies.
• Enable real-time features with WebSockets:
  use NestJS Gateways/Socket.IO or ws for presence, notifications, and fan-out at scale; secure and rate-limit connections.
• Use Redis/Valkey effectively:
  design cache keys/TTLs, apply cache-aside/write-through, implement distributed locks, queues/streams, pub/sub, and mitigate hot keys.
• Containerize and run locally:
  craft efficient multi-stage Docker builds, add healthchecks, and orchestrate multi-service dev stacks with docker-compose.
• Quality & reliability:
  write unit/integration/e2e tests (Jest/Supertest), add schema validation (class-validator/OpenAPI), and instrument with logs/metrics/traces.
• Collaborate across teams:
  review PRs, write concise design docs, and partner with product, frontend, and data to deliver measurable outcomes.

Requirements:

• 5+ years building backend systems; 3+ years NestJS + TypeScript in production.
• Strong Docker and docker-compose skills (multi-stage builds, image slimming, healthchecks).
• Solid microservice design: domain boundaries, API versioning, idempotency, saga/choreography, and eventual consistency (outbox/inbox).
• Hands-on JWT implementation in distributed systems.
• Demonstrated payment experience (idempotency keys, reconciliation jobs) and webhooks (HMAC/signatures, replay protection, retries).
• Built and scaled WebSockets features in production.
• Proficiency with Redis/Valkey for caching and real-time patterns; strong SQL fundamentals (PostgreSQL/MySQL) and practical ORM experience (TypeORM/Prisma).
• Testing mindset with meaningful coverage and CI checks; working knowledge of security best practices (OWASP, secrets management, least privilege).
• Comfortable with telemetry (structured logs, metrics, tracing) and on-call ownership.

Nice to have:

• Kong Gateway
  (or similar API gateway) for routing, auth, rate limiting, and observability.
• Kubernetes/Helm; service meshes (Istio/Linkerd).
• Event platforms (NATS/Kafka/RabbitMQ) and streaming patterns.
• GraphQL (Apollo/NestJS) including subscriptions.

We offer*:

• Flexible working format - remote, office-based or flexible
• A competitive salary and good compensation package
• Personalized career growth
• Professional development tools (mentorship program, tech talks and trainings, centers of excellence, and more)
• Active tech communities with regular knowledge sharing
• Education reimbursement
• Memorable anniversary presents
• Corporate events and team buildings
• Other location-specific benefits
• not applicable for freelancers