Andrii Z.

Senior Go engineer, 10+ years shipping production backends for US teams. I build Go services that stay correct under load — PostgreSQL-backed, event-driven and observable — with enough React depth to take a feature from schema to screen. Right now I'm a Senior Full-Stack Go Developer at Teladoc Health (HIPAA-regulated telehealth): • Built a production Go service that matches patients with available doctors for on-demand visits — no double booking via PostgreSQL invariants and SKIP LOCKED across replicas, live queue position over SSE (8 ms p99), visit events to Kafka via a transactional outbox, 0 invariant violations under chaos testing with replica crashes. • Replaced two legacy registration services with one server-driven UI service serving web, iOS and Android from a single JSON contract — changes ship without app-store review; daily registrations up ~10%. • Migrated account creation and OTP verification to Keycloak and added Google / Apple sign-up via identity brokering. Before that: • Purple Carrot — Braintree payments (Apple Pay, Google Pay, Venmo) behind a unified payments layer with refunds and CCPA deletion; server-side A/B testing that lifted sign-up conversion; CloudFront cutting load time ~20%. • Seniorlink — integrated a Go file-management microservice with a concurrent, re-runnable migration; built an OAuth2 token layer hardened against concurrent-refresh races; designed an Avro-schema event pipeline over RabbitMQ; led a jQuery → React migration (~100 components). WHERE I'M STRONGEST • Go (Golang) — concurrent services and workers (Asynq), REST / gRPC APIs, graceful shutdown, table-driven tests. • PostgreSQL — data invariants, row locking (SKIP LOCKED), migrations, query tuning. • Event-driven systems — Kafka, RabbitMQ, transactional outbox, Avro, idempotent consumers. • Auth — OAuth2 / OIDC, Keycloak, identity brokering, social sign-up. • Frontend — React / Redux, TypeScript, incremental legacy migrations. • Supporting cast — Docker, Redis, AWS, Elasticsearch, Jenkins. • AI-assisted development — Cursor, Copilot and Claude are part of my workflow, not a substitute for review. HOW I WORK I look for the simplest thing that solves the business problem, ship in small reviewable pieces, and flag slippage early rather than at the deadline. Comfortable with US-hours overlap. If you're weighing a few candidates, I'm happy to start with a small paid task so you can see how I work before committing to anything larger.