Backend Engineer

Senior Backend Engineer with 8+ years of experience building and operating production backend services, ideally in Node.js, TypeScript, Go, and PostgreSQL.

They should be skilled in distributed systems, queues, asynchronous processing, API and relational database design, AWS infrastructure, infrastructure as code, observability, deployments, and production debugging.

The candidate should be familiar with owning features end-to-end, designing and scaling reliable services, handling retries and failures, performing safe database changes, participating in on-call, and collaborating with customers and cross-functional teams.

How would you design a reliable email delivery pipeline using queues and background workers?

I would separate API ingestion from delivery using durable queues, idempotent jobs, and workers with bounded concurrency. The system should support exponential backoff, dead-letter queues, visibility timeouts, and clear delivery state transitions for retries and failures.

How would you make email delivery jobs idempotent in the presence of retries and duplicate events?

I would assign each delivery a stable idempotency key and enforce uniqueness at the database or workflow boundary. Workers would check and atomically update delivery state so repeated messages cannot send the same email more than once.

How would you scale a Node.js and TypeScript API handling millions of requests?

I would keep API instances stateless, scale them horizontally, and move slow work to asynchronous workers. I would also use connection pooling, caching where appropriate, efficient serialization, rate limiting, and metrics to identify bottlenecks.

How would you diagnose and optimize a slow PostgreSQL query?

I would inspect query plans with EXPLAIN ANALYZE, review indexes, joins, filters, and row estimates, and check for lock or connection-pool contention. I would then test targeted changes against representative data before deploying them safely.

How would you perform a safe database schema migration on a large production table?

I would use backward-compatible, expand-and-contract migrations: add nullable structures first, deploy code that supports both versions, backfill incrementally, and remove old structures only after validation. I would monitor locks, latency, replication lag, and migration progress throughout.

What observability would you implement for an email-sending service?

I would track metrics such as request latency, queue depth, processing latency, delivery success and failure rates, retry counts, bounce rates, and provider responses. Structured logs, distributed traces, dashboards, and actionable alerts would support debugging without exposing sensitive email content.

How would you design retries for transient email provider failures?

I would classify errors into transient and permanent categories, retry transient failures with exponential backoff and jitter, and cap attempts to prevent infinite processing. Permanent failures would be recorded immediately, while exhausted jobs would move to a dead-letter queue for investigation.

How would you deploy a backend service safely on AWS?

I would provision infrastructure with Terraform or AWS CDK, use immutable versioned deployments, automated tests, health checks, and gradual rollouts such as canaries. Monitoring and an explicit rollback strategy should be in place before increasing traffic.

How would you design a public API for sending emails?

I would define consistent resource models, authentication, validation, pagination, error formats, rate limits, and idempotency behavior. The API should be versioned carefully and documented with predictable semantics so developers can integrate and troubleshoot it easily.

How would you investigate a production incident involving delayed email delivery?

I would first assess impact using dashboards and traces, then check queue depth, worker health, provider responses, database performance, and recent deployments. I would mitigate quickly through scaling, rollback, or traffic control, communicate status clearly, and follow up with a root-cause analysis and preventive improvements.

Resend is a fast-growing, fully remote developer email platform used by more than 4 million developers, and is hiring a Backend Engineer to help support millions of emails every day. You’ll own features end-to-end, build reliable distributed systems, scale APIs and databases, operate production services, and collaborate closely with customers and support. The stack includes Node.js, TypeScript, Go, Postgres, AWS, Terraform, and AWS CDK. This Americas- or Europe-timezone role offers full remote flexibility, occasional travel, and a $140,000–$180,000 USD salary—an excellent opportunity to shape a high-quality product with meaningful ownership, autonomy, and a talented global team.