Senior Engineer ()

Kyiv - Ukraine

Monthly Salary: Not Disclosed

Posted on: 30+ days ago

Vacancies: 1 Vacancy

Job Summary

Our client is one of Europes fastest-growing mobile companies with 5 million active customers 1000 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/ 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

Required Experience:

Senior IC

Our client is one of Europes fastest-growing mobile companies with 5 million active customers 1000 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 k...