Backend Software Engineer (Node.js)

Senior Backend Software Engineer suitable for an independent, ownership-driven engineer with 5+ years of professional Node.js and TypeScript experience, including 3+ years with SQL databases such as PostgreSQL. The role requires skills in secure API and service development, web security, debugging, defensive programming, Git, Linux, Docker, and reliable scalable system design. The candidate should be familiar with building and maintaining backend services for connected devices or infrastructure products, investigating production issues, contributing to architecture, reviewing code, and collaborating across embedded, cloud, web, and mobile teams.

How would you design a scalable Node.js and TypeScript backend service for UniFi OS devices?

I would separate transport, business logic, and persistence layers, define clear contracts, and use asynchronous, non-blocking operations. I would also design for limited device resources, graceful failure, observability, secure defaults, and backward-compatible API evolution.

How does Node.js handle concurrency, and what can cause performance problems in a backend service?

Node.js uses an event loop for non-blocking I/O, while some operations are delegated to the operating system or worker pool. CPU-heavy work, synchronous APIs, inefficient queries, excessive serialization, and unbounded concurrency can block the event loop and reduce throughput.

How would you structure error handling and defensive programming in a TypeScript service?

I would validate inputs at service boundaries, use typed error categories, handle expected failures explicitly, and avoid leaking internal details. Unexpected errors should be logged with context, produce safe responses, and trigger appropriate alerts or recovery mechanisms.

How would you design and optimize a PostgreSQL data model for a backend service?

I would model data around access patterns, enforce integrity with constraints and transactions, and add indexes based on measured query plans. I would use migrations, parameterized queries, connection pooling, and monitoring to detect slow queries and lock contention.

What steps would you take to secure a REST API handling device and user data?

I would apply strong authentication and authorization, validate and sanitize input, use TLS, protect secrets, implement rate limiting, and avoid exposing sensitive information in responses or logs. I would also address OWASP risks such as injection, broken access control, CSRF, and insecure configuration.

Explain how OAuth works and how you would use it in this platform.

OAuth delegates authorization through access tokens issued by an authorization server, allowing clients to access specific resources without sharing user credentials. I would validate token signatures, issuer, audience, expiration, and scopes, and use short-lived tokens with secure refresh-token handling.

How would you investigate a production issue affecting UniFi gateways or other connected devices?

I would first establish the scope and impact using metrics, logs, traces, and recent deployment information. I would reproduce the failure where possible, isolate whether it is device, service, network, or database related, mitigate customer impact, and then ship a tested fix with a follow-up root-cause analysis.

What observability practices would you implement for Node.js services?

I would use structured logs with correlation IDs, service-level metrics such as latency, error rate, throughput, and resource usage, plus distributed tracing where appropriate. Dashboards and alerts should focus on user impact and meaningful thresholds rather than excessive low-value notifications.

When would you choose gRPC instead of a REST API for internal services?

gRPC is useful for strongly typed, low-latency internal communication with efficient binary serialization and streaming support. REST may be preferable for public APIs, browser compatibility, simpler debugging, and broad client interoperability.

How would you improve the reliability of a Docker-based Node.js service and its delivery pipeline?

I would use minimal pinned base images, multi-stage builds, non-root containers, health checks, and reproducible dependency installation. CI/CD should run linting, type checking, unit and integration tests, security scans, image publishing, and controlled deployments with rollback support.

Ubiquiti is hiring a Backend Software Engineer (Node.js) in Prague to help power the UniFi OS platform for gateways, NAS, and NVR products. You’ll design and maintain secure, scalable services and APIs using Node.js, TypeScript, PostgreSQL, Git, Linux, and Docker while solving complex reliability and production challenges. This is a hybrid role requiring at least two days per week in the Prague office, with a competitive salary, performance bonuses, five weeks of vacation, flexible hours, and home-office options. Apply to shape the future of connectivity alongside a talented engineering team with minimal bureaucracy and excellent benefits.