API Documentation with Postman Collection

A developer spends up to 3 hours per day checking endpoints against outdated documentation. A Postman (software) Collection reduces this to 15 minutes. We created a collection for a project with 200+ endpoints: after deployment, the number of bugs per release dropped by 40%. Our experience — 10+ years in development and 50+ API documentation projects. Average budget savings on testing — 30%, ROI less than 3 months. Get a consultation on your API — contact us.

How a Postman Collection Solves the Problem of Outdated Documentation

Outdated documentation is a common pain: endpoints change, parameters become obsolete, and developers spend hours debugging. A Postman Collection is a living document: you immediately execute requests, see real responses, and automatically check statuses. We guarantee that after delivery the collection will match the API — we use auto tests that validate every endpoint. A collection is a set of saved requests organized into folders.

Structure and Key Elements — Documenting API with Postman

{
  "info": {
    "name": "MyApp API",
    "schema": "https://schema.getpostman.com/json/collection/v2.1.0/collection.json"
  },
  "variable": [
    { "key": "base_url", "value": "https://api.example.com/v1" },
    { "key": "token", "value": "" }
  ],
  "item": [
    {
      "name": "Auth",
      "item": [
        {
          "name": "Login",
          "request": {
            "method": "POST",
            "url": "{{base_url}}/auth/login",
            "header": [{ "key": "Content-Type", "value": "application/json" }],
            "body": {
              "mode": "raw",
              "raw": "{\"email\": \"[email protected]\", \"password\": \"secret\"}"
            }
          },
          "event": [{
            "listen": "test",
            "script": {
              "exec": [
                "pm.test('Status 200', () => pm.response.to.have.status(200));",
                "const json = pm.response.json();",
                "pm.collectionVariables.set('token', json.data.token);"
              ]
            }
          }]
        }
      ]
    }
  ]
}

pm.collectionVariables.set — key pattern: the login test automatically saves the token, all subsequent requests use {{token}} in the Authorization header.

What Elements Make a Collection a Living Document?

Environments — Different Environments

{
  "name": "Production",
  "values": [
    { "key": "base_url", "value": "https://api.example.com/v1", "enabled": true },
    { "key": "token", "value": "", "enabled": true }
  ]
}

Separate files env.development.json, env.staging.json, env.production.json — switched in Postman via dropdown. Templates without values are committed to the repository, files with secrets are not. For sensitive data, use CI system variables instead of storing them in the collection.

Pre‑request Scripts and Auto‑tests

Pre‑request scripts run before each request. Example — automatic token refresh:

const tokenExpiry = pm.collectionVariables.get('token_expiry');
if (!tokenExpiry || Date.now() > parseInt(tokenExpiry)) {
    pm.sendRequest({
        url: pm.variables.get('base_url') + '/auth/refresh',
        method: 'POST',
        header: { 'Content-Type': 'application/json' },
        body: {
            mode: 'raw',
            raw: JSON.stringify({ refresh_token: pm.collectionVariables.get('refresh_token') })
        }
    }, (err, res) => {
        pm.collectionVariables.set('token', res.json().data.access_token);
        pm.collectionVariables.set('token_expiry', Date.now() + 3600000);
    });
}

Such a script ensures the token is always up‑to‑date — even during long testing sessions.

What Mistakes Are Made When Creating a Postman Collection?

• Missing environment variables — you'll have to change URL in every request.
• No pre‑request scripts for token refresh — tests will fail after session expiration.
• Tests only check status code — add JSON schema validation using pm.response.to.have.jsonSchema.
• Collection not versioned — store it in Git alongside code.
• Newman not configured in CI — tests don't run automatically after deployment.

What Is Included in Turnkey API Documentation?

We provide:

• Ready‑made Postman Collection (structure, variables, example responses).
• Environments for all environments (dev/staging/production).
• A set of auto‑tests with status and response schema checks.
• Pre‑request scripts for automatic authentication.
• Integration with CI via Newman (GitHub Actions, GitLab CI).
• Publication of documentation on Postman API Network.
• Team training on working with the collection.

Order development of a Postman Collection and get up‑to‑date documentation with auto‑tests.

Comparison: Postman Collection vs OpenAPI

Postman Collection is better suited for quick testing and debugging, especially in team work. However, OpenAPI is useful for generating clients and servers.

Process and Timeline

Timeline: basic collection (20–30 endpoints) — 1–2 days. With integration and publication — 1 additional day. Exact timeline calculated after audit.

Step‑by‑Step Guide for Setting Up Newman in CI

1. Install Newman globally: npm install -g newman.
2. Create a newman-run.js file with commands to run.
3. In CI config (GitHub Actions) add a step:

- name: Run API Tests
  run: |
    newman run collection.json \
      --environment env.ci.json \
      --bail failure

4. For reports, use --reporters cli,json.
5. Schedule a run after each deployment.

--bail failure stops the run on the first error — convenient for smoke tests after deployment.

Why Choose Us?

Over 10 years of experience in API development and 50+ documentation projects. We guarantee the collection is up‑to‑date and ready for immediate use. Investment in creating a Postman Collection pays off: average budget savings on testing is 30%. Get a consultation on your API — contact us.

API Development with REST, GraphQL, WebSocket, and tRPC

A client comes to us with a Postman collection of 200 endpoints and says: 'Everything works, but the frontend is slow.' We open the Network tab — 47 sequential requests to load one dashboard page. Each one waits for the previous. This is not a server speed issue — it's an API architecture problem. With 10 years on the market, we've redesigned dozens of such integrations, and we guarantee: the right protocol and contract solve the problem at its root.

When REST stops being enough

REST works well for simple CRUD operations. But as soon as a mobile app appears alongside the web interface, over-fetching begins: the mobile app requests /api/users/123 and gets a 4KB object, but only needs name and avatar. Multiply that by a list of 50 users — 200KB traffic instead of 8KB.

GraphQL solves this with selection sets. The client describes exactly the fields it needs, and the server returns only those. On a project with React Native + Next.js, we migrated from REST to Apollo Server: payload size on the main screen dropped from 340KB to 28KB — a 92% traffic savings. Our certified engineers confirm: the typical pain when adopting GraphQL is N+1 query. A resolver for the author field on a post calls SELECT * FROM users WHERE id = ? for each post in the list. On a page with 20 posts — 21 database queries. Solved with DataLoader — it batches queries and turns them into one SELECT * FROM users WHERE id IN (...).

What is tRPC and how is it better than REST/GraphQL?

If the entire stack is TypeScript (Next.js + Node/Bun), tRPC removes a whole layer of problems. You define a procedure on the server — the client gets full type-safety automatically, without code generation and without Swagger. Renamed a field in the Zod schema — TypeScript highlights all places on the frontend where it's used. tRPC reduces code by 2 times compared to REST + Swagger + openapi-typescript: no need to maintain a separate specification and generate types — everything is inferred from runtime validators. However, tRPC is not suitable if the API is consumed by third-party clients or mobile apps in other languages — in such cases we use GraphQL or REST with OpenAPI specification.

WebSocket and real-time: when SSE, when WS?

HTTP polling every 5 seconds is an illusion of real-time with up to 5 seconds delay and useless server load. For chats, live notifications, collaborative editing — WebSocket or Server-Sent Events. SSE is a one-way stream from server to client, works over ordinary HTTP, automatically reconnects. Suitable for notifications, data streaming, progress bars. WebSocket is bidirectional, needed for chats and collaborative features. Experience shows: 80% of 'real-time' tasks are solved with SSE, not WebSocket — fewer infrastructure complexities.

A typical mistake: opening a WebSocket connection for each page component. On one project, the dashboard opened 12 parallel WS connections. The correct approach is one connection manager at the application level, subscriptions through it. In our work results, we always transfer the connection scheme and a ready solution.

Swagger / OpenAPI as a contract

Documentation written after the fact becomes outdated the day after release. We write the OpenAPI 3.1 specification before development starts; it becomes the contract between frontend and backend. The frontend generates types via openapi-typescript, the backend validates incoming data using generated schemas. Contract deviation from implementation is caught on CI, not during review. For Laravel — l5-swagger or dedoc/scramble. For Node.js — @fastify/swagger or Zod + zod-to-openapi.

How to properly authenticate an API?

JWT with long-lived access tokens without rotation is a source of problems when compromised. The correct scheme: access token for 15 minutes, refresh token for 30 days with rotation on each use. Refresh token stored in an httpOnly cookie, access token in memory (not in localStorage). For inter-service communication — API Keys with scope limitations or mTLS. OAuth 2.0 with PKCE for public clients (SPA, mobile).

How to handle versioning and backward compatibility?

Breaking changes in an API without versioning break clients. Three approaches we use in projects:

We guarantee backward compatibility through automated checks (oasdiff) on CI.

How we develop APIs: step-by-step plan

1. Analysis — audit of current integrations, data schema compilation, protocol selection (REST/GraphQL/tRPC/WebSocket).
2. Contract design — OpenAPI or SDL (GraphQL) before the first line of code.
3. Development — implementation per contract, unit tests for each endpoint.
4. Load testing — k6: 500 virtual users, 10 minutes, p95 latency ≤ 200ms.
5. Deployment — CI/CD with backward compatibility check, automatic documentation publication.
6. Team training — handover of Postman collection or Playground, connection instructions.

What is included (deliverables)

• OpenAPI 3.1 specification (or SDL for GraphQL).
• Generated client types for TypeScript / Dart / Kotlin.
• Set of automated tests covering all endpoints (unit + integration).
• Load tests (k6) and report (p50/p95/p99 latency, RPS).
• Documentation in Swagger UI / Redoc / GraphiQL.
• Team training (2–4 hour workshop).
• Support for 30 days after delivery (per contract).

Our experience

• 10+ years in the API development market.
• 200+ completed projects (REST, GraphQL, WebSocket, tRPC).
• 50+ certified engineers (AWS, Kubernetes, API Design).
• Traffic savings averaging 85% when migrating from REST to GraphQL for mobile apps.
• 100% backward compatibility — not a single broken client in the last 3 years.

Timeline

API development for a typical SaaS project with 30–50 endpoints: from 3 to 8 weeks depending on business logic complexity and number of external integrations. Migration of an existing REST API to GraphQL: from 2 to 6 weeks. Adding a WebSocket layer to an existing backend: from 1 to 3 weeks. Cost is calculated individually after an audit. Get a consultation — contact us to discuss your project.