How Can We Use JWT Tokens for Fine-Grained Authorization Without Token Bloat?

I wouldn't worry too much about bloating the token unless you're adding a lot of claims. Base64 encoding is quite efficient. However, if you have a complex setup with many microservices and potentially hundreds of permissions, the token could get large quickly. Imagine needing to encode 400 privilege strings! That could balloon the size up to 27 KB, which is substantial for a token.

One approach you could consider is keeping permissions separate from the JWT itself. On the front end, you could request user permissions when retrieving user info and store them in your application's state. On the backend, always recheck permissions and append them to the request context as needed.

Ultimately, the right choice comes down to trade-offs based on your use case. If you include permissions in the JWT, you'll have faster reads since everything's in one place. But keep in mind, this could lead to issues with token size and real-time updates when permissions change. On the other hand, querying the auth service for permissions means you're always getting the latest data, but adds latency to each request. Caching role-to-permission mappings locally could strike a balance if done carefully.