Senior Fullstack Engineer (TypeScript, API, ReactJS)

Top 3 reasons to join us

• Work in fast-growing startup
• Serve passionate and active sports users
• Meaningful mission and impact

Job description

Build across the API and web application, taking features end to end or delivering stable APIs and product surfaces for other engineers to build on. The role focuses on dependable third-party integrations, asynchronous work, performance, and shared product patterns.

Scope of Job

• Design stable API contracts for internal screens and other engineers.
• Integrate payment, messaging, storage, and partner services, handling rate limits, retries, timeouts, webhooks, and production failure modes.
• Deliver features from API contract through to polished Next.js screens that cover all states.
• Build queue-based workers, background jobs, callbacks, notifications, imports, exports, and external-system syncs.
• Improve response shapes, caching, payload size, and web performance.
• Establish shared components and patterns across customer-facing and internal admin tools.

Key Success Indicators for this Role

• Delivers stable, well-designed APIs that internal product surfaces and other engineers can reliably build on.
• Ships end-to-end features that handle real-world states beyond the happy path.
• Improves the reliability and performance of integrations, asynchronous workflows, and web experiences.

Your skills and experience

Must Have

1. Professional Expertise (Hard Skills & Experience):

• 5+ years building and operating production web applications across APIs and browsers.
• Deep TypeScript experience; able to become productive quickly with Bun and Elysia.
• Strong API design judgment across resource modelling, versioning, pagination, error contracts, idempotency, and authentication.
• Experience with third-party and partner API integrations, including authentication, webhooks, retries, rate limits, timeouts, and production failure modes.
• Experience with queues, background jobs, and idempotent workers.
• Practical caching knowledge, including cache placement and invalidation.
• Self-sufficient SQL skills for modelling straightforward domains and writing queries.
• Security fundamentals: authentication, authorization, session and token handling, input validation, and common web attack surfaces.
• Deep Next.js and React knowledge, including server components, SSR, static rendering, and client rendering.

2. Communication & Documentation:

• Designs API contracts with the needs of their consumers in mind.
• Collaborates effectively across API and frontend work to deliver complete product experiences.

3. Personality & Behavioral Traits:

• Moves between backend and frontend work without friction.
• Takes ownership of features end to end and considers real-world states, not only the happy path.
• Cares about how the product looks and feels, closing gaps between mockups and production-ready screens.

4. Culture & Career:

• Contributes to shared components and product patterns that make future work faster and more consistent.
• Balances reliability, performance, and product quality across customer-facing and internal tools.

Nice to Have

• Experience with event-driven or queue-based distributed systems.
• Production experience with realtime transport such as MQTT or an equivalent pub/sub broker.
• Deep PostgreSQL knowledge, including query plans, indexing strategy, and schema migrations on live systems.
• Production experience with Redis, DragonflyDB, ClickHouse, or other data stores beyond PostgreSQL.
• Deep Next.js App Router knowledge, including server actions, streaming, caching, and revalidation.
• Experience with web performance tooling, including Core Web Vitals, bundle analysis, image optimization, and font optimization.

Why you'll love working here

• 100% salary during probation
• Competitive salary + 13th-month bonus
• Annual salary review
• Premium health insurance from Bao Viet after probation
• Transportation support
• Lunch, coffee, and snacks
• All statutory benefits per Vietnamese Labor Law