Optimization of Permission Retrieval to Avoid Header Size Issues and Management API Rate Limiting

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Hello Auth0 Support Team,

I am currently facing a challenge regarding the size of our OIDC tokens. Due to the high number of permissions assigned to our users, the access token size is exceeding HTTP header limits, causing failures in our downstream services.

To mitigate this, I have attempted to retrieve user permissions directly via the Management API (/api/v2/users/{id}/permissions). However, this approach has introduced a new bottleneck: Rate Limiting. Since we need to perform these lookups frequently and handle pagination for users with extensive permission sets, we are hitting the API quotas too quickly.

I would like to inquire about best practices or alternative architectural patterns for the following:

  1. Efficient Permission Retrieval: Is there a way to fetch all assigned permissions for a user in a single call or a more optimized manner than standard page-based polling?

  2. Filtering Capabilities: Does the Management API support filtering permissions via Regex or specific patterns server-side to reduce the payload and the number of requests?

  3. Alternative Storage/Querying: Beyond the app_metadata (which also has size constraints) or the standard permissions endpoint, is there a recommended way to synchronize or cache these permissions to avoid frequent Management API hits?

Our goal is to decouple the permission set from the JWT while maintaining a performant and scalable authorization flow.

Looking forward to your guidance on this.

Best regards,

3

Hi @edison.rojas,

Welcome to the Auth0 Community!

The Management API is designed for administrative tasks, not for high-frequency runtime authorization checks.

  • Header Limits: Most web servers (like Nginx or Apache) cap headers at 8KB or 16KB.
  • Rate Limits: The /api/v2/users/{id}/permissions endpoint is subject to strict production rate limits that are not intended to support per-request lookups from your application’s backend.
  • Pagination: The Management API does not currently support server-side Regex filtering for permissions; it only supports standard pagination (page and per_page), which compounds the rate-limiting issue.

To decouple permissions from the JWT while remaining performant, I recommend moving away from real-time Management API calls in favor of a Cache-Aside or External Authorization pattern.

1. The Token Exchange / Cache-Aside Pattern

Instead of fetching permissions from Auth0 on every request:

  1. On Login: Use an Auth0 Action to send the user’s permissions to your own database or a fast cache (like Redis) only once during the authentication flow.
  2. On Request: Your downstream services see the sub (User ID) in the Access Token and query your Redis/Database for permissions. This keeps the JWT small and moves the “heavy lifting” to your infrastructure where you have unlimited scaling.

2. Selective Claim Scoping

If you must keep permissions in the token, use Actions to filter them so only the permissions relevant to the specific API being called are included.

exports.onExecutePostLogin = async (event, api) => {
  // Logic to only include permissions matching a specific prefix/service
  const relevantPermissions = event.user.permissions.filter(p => p.startsWith('service_a:'));
  api.accessToken.setCustomClaim('https://myapp.com/permissions', relevantPermissions);
};

3. Management API Optimization

If you must use the Management API for background syncing:

  • Caching: Implement a TTL (Time-to-Live) cache on your server. Do not fetch permissions if you’ve fetched them for that user within the last 5–10 minutes.
  • Batching: If you are syncing data, use the Export Job feature for bulk data rather than individual calls.

If you have any further questions, please don’t hesitate to reach out.

Have a good one,
Vlad