API_KEY vs Service Account ( JWT )

When should you use API key and when should you use a service account?

Most of the time people tend to go for the API_KEY because its simpler. But using a service account – JWT – is more beneficial and it is really worth the time you put in setting it up.

Basically, you can use API keys for quick testing or public access but for more rigorous tasks you should almost always set up a service account.

Here is the drilldown:

API Key Limitations 🗝️

1. No Authentication
   • Only identifies your project, not who’s making the request
   • Anyone with the key can use it (risk of quota theft if exposed)
2. No Fine-Grained Permissions
   • Cannot restrict access to specific resources (e.g., only allow tagging for certain folders)
3. Rate Limits
   • Stricter default quotas (e.g., 1,800 requests/minute vs 15,000 with JWT)
4. No User Impersonation
   • Cannot act on behalf of users (always acts as “anonymous”)
5. No Audit Logs
   • Harder to track who made requests in Google Cloud logs

JWT (Service Account) Limitations 🔐

1. Complex Setup
   • Requires generating RSA keys and handling token expiration (~1 hour)
2. Private Key Security
   • Leaked keys grant full access to the service account’s permissions
   • Must be securely stored (use Google Secret Manager in production)
3. Initial Latency
   • Each JWT must be generated and exchanged for an access token (~300ms overhead)
4. Scope Restrictions
   • Must pre-define OAuth scopes (e.g., https://www.googleapis.com/auth/cloud-vision)
5. Project-Level Access
   • By default, can access all resources the service account has permissions for

When to Use Each

Key Differences Table

to wrap up:

• Use JWT if you need:

  • Higher quotas

  • Audit trails

  • To restrict access to specific Cloud Storage buckets/folders

• Use API Key only for:

  • Quick testing

  • Publicly accessible images

  • When you don’t need IAM controls

Detailed comparison

const visionUrl = `https://vision.googleapis.com/v1/images:annotate?key=YOUR_API_KEY`;
// No auth headers needed

const {JWT} = require('google-auth-library');
const jwtClient = new JWT(
  serviceAccount.client_email,
  null,
  serviceAccount.private_key,
  ['https://www.googleapis.com/auth/cloud-vision']
);

// Auto-refreshes tokens
const tokens = await jwtClient.authorize();