API & Systems Integration
API integration is the skill of connecting systems that were not designed for each other and keeping the result reliable. It is assessed on failure handling — the integration works on the happy path for everyone, so the happy path measures nothing.
Also called: backend integration, third-party APIs, systems integration
What is api & systems integration?
This covers reading unfamiliar API documentation, handling rate limits, retries, timeouts and partial failures, designing idempotent operations, and managing credentials safely.
Integrations fail in production, at 3am, in ways that corrupt data. The engineer who designed for idempotency in the first hour saves days later, and that judgment is straightforward to measure.
What do the levels of api & systems integration mean?
Four levels, each defined by observable behaviour rather than by years. This is the definition employers set their bar against, and the one every proof is scored to.
- L1Aware
Can call a documented API and parse the response correctly.
Evidence: A working integration against a straightforward API.
- L2Working
Handles errors, retries, and rate limits, and manages credentials without leaking them.
Evidence: An integration with retry and backoff, credentials held in config.
- L3Independent
Designs for idempotency and partial failure, and makes state recoverable when the remote system misbehaves.
Evidence: An integration with idempotency keys and a documented recovery path.
- L4Leading
Sets integration patterns and builds abstractions that make correct handling the default for other engineers.
Evidence: A shared integration layer used across services.
| Level | Label | People proven here |
|---|---|---|
| L1 | Aware | 0 |
| L2 | Working | 0 |
| L3 | Independent | 3 |
| L4 | Leading | 1 |
How is api & systems integration assessed?
Candidates integrate against a documented API with deliberately awkward behaviour — rate limits, partial failures, non-idempotent endpoints. Scoring is weighted heavily toward failure handling and safe credential management.
Which roles require api & systems integration?
| Role | Level required | Status |
|---|---|---|
| AI Builder | L2 Working | Nice to have |
| AI Engineer | L3 Independent | Required |
| Founding Engineer | L3 Independent | Required |
How do you prove api & systems integration?
API & Systems Integration: questions people ask
- Which language do I use?
- Any. The rubric scores failure handling and design, not language idiom. Submit in whatever you are fastest in.
- Can I use AI coding assistance?
- Yes. The rubric targets design decisions an assistant will not make for you — idempotency, recovery, and credential handling.
- Why is failure handling weighted so heavily?
- Because the happy path is where every candidate succeeds, so it carries no signal. Everything that distinguishes engineers happens when the remote system misbehaves.