What is 'Fat Client' vs 'Thin Client' in layering?

Updated Apr 28, 2026

Short answer

Fat clients perform heavy processing on the UI side; thin clients offload most logic to the server middleware.

Deep explanation

Middle-tier architecture often deals with reliability. Using a Circuit Breaker prevents a cascading failure where one slow service bogs down the entire system. Onion architecture ensures the core business logic remains independent of the database or external APIs.

Real-world example

A payment gateway middleware that retries a transaction only if it hasn't been processed yet (Idempotency).

Common mistakes

  • Mixing business logic directly into the middleware, making it hard to test the core domain.

Follow-up questions

  • How does a 'Sidecar' pattern relate to middleware?

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