MIDDLE/SENIOR BACKEND DEVELOPER

3–5 years of backend development experience (Middle) or 5+ years (Senior); proven experience running production services. Proficient in Node.js and at least one additional backend language (Java/Go/.NET/Python); solid understanding of runtime, concurrency, and I/O. Solid knowledge of API design: idempotency, versioning, pagination; hands-on experience with popular frameworks (NestJS/Express/Spring Boot/FastAPI…). Strong SQL skills (PostgreSQL/MySQL): query optimization, indexing, transactions & isolation; NoSQL (Redis/MongoDB) is a plus. Experience with event systems & message queues (Kafka/RabbitMQ/SQS); understanding of event-driven design, saga/outbox, and eventual consistency. Good knowledge of security: OAuth2/OIDC, RBAC/ABAC, TLS, input validation; preventing SQLi/XSS/SSRF. Basic DevOps skills: Git, CI/CD (Jenkins/GitHub Actions/GitLab), Docker; Kubernetes and cloud experience (AWS/GCP/Azure) preferred. Strong analytical, problem-solving, and clean coding skills; writing unit/integration/contract tests and clear documentation. English: strong reading comprehension and capable of communicating in technical discussions (meetings, chat, email). PREFERENCES Experience with microservices: service discovery, circuit breaker, retry/backoff; observability (logging/tracing/metrics). High-performance architecture: strategic caching, CQRS, partitioning/sharding, read replicas. Production operations experience: on-call, RCA/postmortem. Contributions to open-source projects, real-world products/services, or cloud certifications. Experience with web3 (smart contracts, wallet integration, Web3.js/Ethers.js, on-chain/off-chain transactions) is a plus.