Senior Backend Engineer

This role is ideal for a Senior Backend Engineer with 5+ years of experience, strong expertise in Python, PostgreSQL, Docker, and AWS (S3, SQS), plus solid testing skills using Pytest. The position focuses on building and maintaining scalable backend services, ensuring reliability, and occasionally providing full-stack support for international client projects. It suits someone based in LATAM who thrives in remote, collaborative environments, values clean, test-driven code, and is eager to grow with exposure to infrastructure as code, FastAPI/Tornado, Kubernetes, and observability tools.

1. How would you design an idempotent API that writes to PostgreSQL and enqueues a message to SQS?
   Use a client-supplied Idempotency-Key stored in a unique column; wrap the DB write and an “outbox” record in one transaction, then a worker publishes to SQS and marks the outbox processed. On retries, return the prior result.

2. What are best practices for structuring a FastAPI/Tornado service at scale?
   Separate routers/handlers by domain, use Pydantic models for validation, dependency injection for DB/clients, and async SQLAlchemy with a pooled, per-request session. Add health checks, middlewares, and settings via pydantic-settings.

3. How do you tune PostgreSQL queries in a high-throughput service?
   Use EXPLAIN ANALYZE to find bottlenecks, add selective/composite indexes, prefer keyset pagination over OFFSET, and leverage UPSERT (ON CONFLICT) with proper unique keys. Monitor with query stats and fix N+1 at the ORM layer.

4. How would you process SQS messages reliably at scale?
   Set visibility timeout > max processing time, implement exponential backoff retries and DLQ, ensure handlers are idempotent, and batch ReceiveMessage/DeleteMessage. Emit structured logs/traces per message for observability.

5. What’s your approach to S3 file handling for large uploads from a web client?
   Use presigned URLs with enforced content type/size, multipart uploads for big files, and server-side encryption (SSE-S3 or KMS). Validate metadata server-side before persisting references in Postgres.

6. How do you containerize a Python backend for fast, secure deployments?
   Use multi-stage builds with slim base images, pin hashes, run as non-root, cache deps via requirements.txt/pip-tools, and add HEALTHCHECK. Externalize config via env vars and mount read-only filesystems where possible.

7. How do you test AWS integrations with pytest and mocker?
   Abstract AWS clients behind interfaces and inject them; use mocker to stub methods and moto/LocalStack for higher-fidelity tests. Provide fixtures for S3/SQS resources and assert side effects plus emitted events.

8. What’s your methodology for TDD and CI in this stack?
   Write failing unit tests first for core logic, add integration tests with ephemeral Postgres (docker) and migrations, then e2e happy paths. CI runs linting (flake8/black), type checks (mypy), tests with coverage gates, and builds the image.

9. How would you implement observability with OpenTelemetry/New Relic?
   Instrument FastAPI ASGI middleware for traces/metrics/logs, propagate context into SQS producers/consumers, and add custom spans around DB queries and external calls. Export to OTLP/New Relic and set SLOs with alerting in CloudWatch.

10. What security practices do you enforce in Python backends?
    Validate all inputs (Pydantic), use parameterized queries, manage secrets in AWS Secrets Manager/SSM, enable strict CORS, and sanitize logs. Add rate limiting, audit trails for sensitive actions, and regular dependency scanning.

ioet is hiring a Senior Backend Engineer (fully remote, LATAM-based) to work on high-impact projects for global clients. You'll build robust solutions using Python, PostgreSQL, Docker, and AWS (S3, SQS), with testing via Pytest and mocker. Bonus if you have experience with FastAPI, Terraform, Kubernetes, or advanced AWS services. This full-time role offers USD compensation, flexible hours, English classes, and a structured career path. Ideal for engineers with 5+ years’ experience and strong English skills seeking professional growth in a collaborative, international team.