Introduction

When integrating external applications with Oracle Integration Cloud (OIC), one of the most secure and scalable authentication mechanisms is OCI IAM Client Credentials OAuth Tokens. However, calling the OCI IAM token endpoint for every API request quickly becomes a performance bottleneck, particularly in high-throughput environments like retail, logistics, finance, or telecom where hundreds of integration calls happen per second.

To solve this, we can use OCI API Gateway with a custom OCI Authorizer Function, which securely retrieves and caches OCI IAM tokens. This ensures that downstream calls to OIC are authenticated efficiently, without hammering the IAM token endpoint.

Real-World Scenario: High-Volume Retail Integrations

A retail enterprise has multiple applications calling OIC integrations for order processing, validation, and shipment updates. Each request must be authenticated using OCI IAM OAuth tokens.

However, generating a new OCI IAM token for every OIC call results in:

  • Repeated IAM round-trips
  • Increased authentication latency
  • Risk of throttling from the IAM endpoint
  • Unnecessary overhead, since tokens typically remain valid for 60 minutes

This is where API Gateway + Authorizer Function comes into play. Introduce an OCI API Gateway in front of OIC and use an Authorizer Function with in-memory token caching.

The full Authorizer Function implementation is available on GitHub.

Why Token Caching Matters

Every request coming to API Gateway must be authenticated. Without token caching:

  • The authorizer would call OCI IAM for every API request.
  • This increases IAM traffic.
  • Adds latency to every OIC call.
  • Can lead to throttling or failures.

With token caching:

  • IAM token is fetched only once per client until it expires
  • Cache lookup is fast (in-memory)
  • Dramatic reduction in token endpoint calls
  • Better throughput for high-volume integration.

How the Authorizer Function Works Internally

The OCI Function performs these steps:

1. Extract Authorization header

Takes the incoming Basic Auth or token from payload and generates a unique cache key (SHA-256 hash).

2. Look up token in cache

If token exists and is not expired, reuse it.

3. If cache is not there, fetch a new OCI IAM token

The function calls:

POST /oauth2/v1/token grant_type=client_credentials scope= {OIC scope}

4. Decode JWT expiry & cache it

Expiry (exp) is extracted from JWT, ensuring accurate cache invalidation.

5. Return the token back to API Gateway

API Gateway uses this for backend authorization to OIC.

Conclusion

Using OCI API Gateway with a custom Authorizer Function that implements token caching significantly improves performance and reduces dependency on OCI IAM for each OIC API invocation. This architecture is ideal for high-volume, latency-sensitive OIC integrations that rely on IAM-based OAuth tokens. If you’re building secure and scalable OIC APIs, this pattern is one of the best practices for efficient authentication handling.