Error Handling Patterns in Rust: From Result to Custom Error Types

"Failures are not exceptions; they are data that must be explicitly carried through system boundaries."

What We're Building

We are implementing a robust error handling strategy for a backend service written in Rust. The scope focuses on evolving from generic Result usage to defining domain-specific error types suitable for production APIs. This process ensures that failure states carry enough context for debugging without leaking sensitive internal details. We will construct a workflow where errors are typed, mapped, and transformed at the application boundary to ensure safety and clarity across the entire stack.

Step 1 — Standard Result Usage

Every function must communicate success or failure clearly using Rust's built-in type. This forces developers to handle potential errors immediately rather than hiding them behind unwrapped values or exceptions.

rust
pub fn fetch_user