Architecture

API-First Development: A Modern Approach to Software Development

Why designing API before implementation speeds up development and improves code quality.


"Backend not ready yet, frontend waiting" - how many times have you heard this? In the traditional model, frontend must wait for backend to deliver endpoints. API-first eliminates this problem entirely.

-40% development time with API-first approach (SmartBear 2023 study)

Traditional approach vs API-First

Code-First (traditional)
  • Backend writes code → generates docs
  • Frontend waits for endpoints
  • Documentation often outdated
  • "This should work differently" mid-project
  • Integration only at the end
API-First
  • Contract first → then implementation
  • Frontend and backend work in parallel
  • Documentation = source of truth
  • API discussions at project start
  • Early integration through mocks

What does the API-First process look like?

Step 1
Design workshop (1-2 days)

Frontend, backend, product owner in one room. Define: what endpoints, what data, what error codes. Leave with draft OpenAPI spec.

Step 2
OpenAPI specification

Formalize draft in YAML/JSON file. Every endpoint, every schema, every example. This becomes the "contract" between teams.

Step 3
Mock server

Generate mock server from OpenAPI spec (Prism, Stoplight). Frontend can start integration immediately - without waiting for backend.

Tools we use

OpenAPI 3.1 specification standard
Stoplight editing + documentation
Prism mock server
Schemathesis contract tests

When does API-First make sense?

1

Distributed team

Frontend in different timezone? API-first allows async work without blocking each other.

2

Public API

If API will be used by external developers - documentation must be perfect from the start.

Want to implement API-First in your team?

We'll run a workshop, help create your first specification, and train your team on the tools.

Category: Architecture
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Tomasz Wróbel

Halo Soft Expert

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