API versioning strategies in Node.js - Step-by-Step Execution

Concept Flow - API versioning strategies

Client sends API request

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Check version info in request

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Route to matching version handler

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Route to matching version handler

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Route to matching version handler

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Use default API version handler

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Send response back to client

The server checks the client's request for version info in URL, headers, or query parameters, then routes to the correct API version handler or defaults.

Execution Sample

Node.js

const express = require('express');
const app = express();

app.get('/api/v1/data', (req, res) => res.send('Data v1'));
app.get('/api/v2/data', (req, res) => res.send('Data v2'));

app.get('/api/data', (req, res) => {
  const ver = req.get('version') || req.query.version;
  if (ver === '1') {
    res.send('Data v1');
  } else if (ver === '2') {
    res.send('Data v2');
  } else {
    res.send('Default data');
  }
});

app.listen(3000);

This code routes requests to different handlers based on the version in the URL path, headers, or query parameters.

Execution Table

Step	Request URL	Version Detected	Handler Chosen	Response Sent
1	/api/v1/data	v1 (from URL path)	v1 handler	'Data v1'
2	/api/v2/data	v2 (from URL path)	v2 handler	'Data v2'
3	/api/data (header: version=1)	v1 (from header)	v1 handler	'Data v1'
4	/api/data (query: ?version=2)	v2 (from query param)	v2 handler	'Data v2'
5	/api/data (no version info)	none	default handler	'Default data'
6	End of requests	-	-	-

💡 Requests stop after all examples are handled.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
version	undefined	v1	v2	v1	v2	undefined	undefined
handler	undefined	v1 handler	v2 handler	v1 handler	v2 handler	default handler	default handler

Key Moments - 2 Insights

How does the server know which API version to use if the version is not in the URL?

The server checks other places like headers or query parameters for version info, as shown in execution_table rows 3 and 4.

What happens if the client does not specify any version?

The server uses a default handler to respond, as shown in execution_table row 5.

Visual Quiz - 3 Questions

Look at the execution table, what version is detected at step 3?

A No version detected

B v2 from URL

C v1 from header

D v2 from query param

💡 Hint

Check the 'Version Detected' column at step 3 in the execution_table.

At which step does the default handler respond?

A Step 2

B Step 5

C Step 4

D Step 1

💡 Hint

Look for 'default handler' in the 'Handler Chosen' column.

If the version was only checked in the URL path, which steps would fail to route correctly?

A Steps 3 and 4

B Steps 1 and 2

C Step 5 only

D All steps would route correctly

💡 Hint

Check which steps detect version from header or query param in the execution_table.

Concept Snapshot

API versioning routes client requests to correct code versions.
Common ways to specify version:
- URL path (e.g., /api/v1/)
- HTTP headers (e.g., 'Accept-Version')
- Query parameters (e.g., ?version=2)
If no version found, use default.
This helps keep old and new API versions working together.

Full Transcript

API versioning strategies help servers handle different versions of an API. The server looks for version info in the request URL path, headers, or query parameters. If it finds a version, it routes the request to the matching version handler. If no version is specified, it uses a default handler. For example, requests to /api/v1/data go to the version 1 handler, while /api/v2/data go to version 2. If the version is in a header or query parameter, the server still routes correctly. This approach allows clients to use different API versions without breaking existing functionality.