Interior mutability

Understanding interior mutability in Rust

This is a medium-difficulty Rust language question that tests your grasp of one of the language's most important escape hatches: how to modify data when the borrow checker would normally forbid it. It appears frequently in systems-programming and trading-infrastructure interviews where Rust is the implementation language.

The question probes whether you understand the distinction between Rust's compile-time guarantees and the runtime flexibility that certain standard-library types provide. A strong answer requires you to know which tool solves which problem, when runtime checks are acceptable, and how to reason about the safety trade-offs involved.

• The borrow checker and mutability rules
• Runtime vs. compile-time enforcement
• Shared ownership and single-threaded vs. multi-threaded contexts
• Panics and invariant violations