10 Rust Interview Questions That Every Developer Should Be Ready For

I’ve been in interviews where a single question separated the hire from the “we’ll keep your resume.” You’ll get asked about Rust not to scare you — to see how you think. Short answers won’t win every time. Explanations will. Talk trade-offs. Talk why you chose what you did. Show a tiny example. Say what you’d do if it failed. This list isn’t trivia. It’s practice for real conversations. Answer like you’ve used Rust in production — even if you haven’t. Sound human. Sound decisive. Sound curious. That’s what interviewers remember. Not the memorized definition. Ten questions with genuine intent, a succinct, interview-ready response, and a helpful tip you can actually give in the room are included here.

A brief personal insight (what interviewers are really looking for), a succinct response that you can recite aloud, and a small piece of advice on how to make your response sound authoritative are all included beneath each question.1) Explain ownership, borrowing, and lifetimes. Why do they matter?

1) Explain ownership, borrowing, and lifetimes. Why do they matter? Personal insight: Interviewers want to know you grasp the mental model Rust enforces.
Answer: Ownership means each value has one owner; moving transfers ownership, cloning copies it. By borrowing (& / &mut), you can make reference to data without taking ownership. The borrow checker enforces lifetimes, which define how long those references remain valid, at compile time to prevent data races and dangling pointers.
Expert advice: Explain that lifetimes are typically inferred by using a brief example (move vs. clone) and that annotations should only be added when required.) Box vs Rc vs Arc — when do you use each?

2) Box vs Rc vs Arc — when do you use each? Personal insight: They’re testing threading and ownership trade-offs.
Answer: Box<T> = heap allocation with single owner. Rc<T> = non-thread-safe reference counting for shared ownership in single-threaded contexts. Arc<T> = atomic reference counting for sharing across threads. Use Weak to avoid cycles.
Pro tip: Mention Weak briefly — it shows you think about leaks.

3) What are Send and Sync? Personal insight: This checks concurrency intuition.
Answer: Send means a value can be transferred to another thread. Sync means references (&T) can be shared across threads safely. Most safe types implement these automatically; unsafe code or raw pointers may break them.
Pro tip: Point out Rc<T> is not Send/Sync but Arc<T> is.

4) How do you handle errors in Rust? Result vs panic! Personal insight: They want to see production judgment.
Answer: Use Result<T, E> for recoverable errors and propagate with ?. Reserve panic! for unrecoverable conditions or programming errors. Structure error types (or use thiserror) so callers can react appropriately.
Pro tip: Talk about converting errors with From or map_err to map low-level errors to domain errors.

5) When do you need explicit lifetimes in function signatures? Personal insight: This is about practical lifetime intuition, not theory.
Answer: When the compiler can’t infer how input lifetimes relate to output lifetimes — often with multiple references where the return references one of them. Elision rules cover simple cases like &self or a single input reference.
Pro tip: Show a tiny signature like fn f<'a>(x: &'a str, y: &str) -> &'a str and explain which input the output ties to.

6) Trait vs trait object (dyn Trait) — static vs dynamic dispatch? Personal insight: They’re probing performance vs flexibility trade-offs.
Answer: Generic traits use static dispatch (monomorphization), which is fast but can increase binary size. dyn Trait uses dynamic dispatch via a vtable and is useful for runtime polymorphism or type erasure. Use impl Trait for ergonomic static dispatch in return positions.
Pro tip: Explain when you’d pick runtime polymorphism (varied types at runtime) vs generics (performance-critical paths).

7) What is unsafe and when is it appropriate? Personal insight: They want to know you respect Rust’s guarantees.
Dereferencing raw pointers, calling unsafe functions, accessing mutable statics, implementing unsafe traits, and FFI are examples of operations that unsafe permits but that the compiler is unable to verify. Use it sparingly, wrap dangerous parts in safe, well-documented abstractions, and keep blocks small.
Pro tip: State the invariant you’re promising whenever you use unsafe.

8) How does async/await work in Rust? What’s an executor? Personal insight: This checks modern concurrency knowledge beyond threads.
Answer: async fn returns a Future — a state machine that does nothing until polled. .await yields while waiting. You need an executor (tokio, async-std, etc.) to run futures. Be mindful of Send bounds when spawning tasks.
Pro tip: Mention Pin only if asked deeper; otherwise keep the focus on Future + executor + Send.

9) The borrow-checker error “cannot borrow x as mutable because it is also borrowed as immutable” has been fixed. My personal opinion: This is a test of practical solutions and debugging.
Answer: Shorten the immutable borrow’s scope so the mutable borrow doesn’t overlap; clone if cheap; restructure code; or use interior mutability (RefCell for single-threaded, Mutex/RwLock for multi-threaded) with care.
Pro tip: Walk through the minimal code change you’d make — interviewers like concrete reasoning.

10) Why are enums + pattern matching powerful? Give an example. Personal insight: They’re checking for idiomatic Rust and API design sense.
Answer: Enums represent finite states and force exhaustive handling with match. Combined with Option and Result, they make invalid states unrepresentable and reduce bugs. Example: match result { Ok(v) => ..., Err(e) => ... }.
Pro tip: Prefer small, domain-specific enums over many booleans — they document intent and reduce edge cases.

Pull quote: “Interviewers don’t want the definition — they want reasoning, trade-offs, and a tiny example.” How to answer like a human (and win)

• Don’t recite textbook definitions. Tie answers to a real problem you solved.
• Offer a one-line example or trade-off. A lengthy lecture is not as memorable as that.
• Explain how you would look into or troubleshoot something if you don’t know. It is important to have practical instincts.

Read the full article here: https://medium.com/rustaceans/10-rust-interview-questions-that-every-developer-should-be-ready-for-c92061252311