Full-stack used to mean one person could ship a feature. Too often it now means the browser is the integration layer.
That is not velocity. That is coupling with a CSS file.
What a BFF is for
A backend-for-frontend is a thin server that speaks product language to the UI and service language to the domain:
- Aggregate the three calls the screen needs into one
- Shape DTOs for the view, not for storage
- Enforce session auth once
- Hide internal IDs, pagination quirks, and partial-failure modes
The React tree should not know that billing lives in service A and entitlements in service B.
Without a BFF, the frontend becomes the org chart
Every new microservice adds:
- Another client SDK in the browser
- Another loading / error state
- Another CORS and versioning story
- Another place to forget a header
You can “move fast” for one quarter. Then every feature is a distributed systems problem in useEffect.
Keep it thin on purpose
A BFF that grows a second domain model is a new monolith with extra hops. Rules of thumb:
- No long-lived business workflows that belong in a domain service
- Mapping and aggregation yes; inventing policy no — call the service that owns the rule
- Version the BFF with the app release when you can; do not forever-support three UI shapes
Full-stack ownership still matters
The win is not “frontend people never touch servers.” The win is one place where the product’s read/write story is coherent — owned by people who care about the screen and the failure modes behind it.
That is full-stack as a delivery model, not as a browser that speaks gRPC-Web to everything.