Interview questions in Go & Rust, page 6
Why must FFI-bound structs use #[repr(C)] and what breaks without it?
Repr(C) fixes field order, size, alignment to C rules for extern calls; omitting it lets Rust reorder or pad fields, causing UB.
Explain the performance overhead of a cgo call
Tests cgo transition penalties and scheduler semantics. A strong answer cites the ~100x overhead (~171ns vs ~1.8ns), notes C blocks an OS thread and starves the scheduler, and warns about memory copy taxes. Red flag: claiming cgo is free or ignoring blocking.
Passing Go/Rust callbacks to a C library
C needs a plain function pointer; in Go use //export with cgo, in Rust an extern "C" fn; carry state via a void* user-data param.
Building a safe Rust wrapper over an unsafe C API
Hide extern calls behind a safe module, own the resource in a struct with Drop calling the C free, return Result mapping C error codes, use NewType/NonNull and PhantomData.
cgo directives: CFLAGS, LDFLAGS, and pkg-config
#cgo CFLAGS feeds the C compiler include paths/defines, LDFLAGS feeds the linker libraries/paths, pkg-config auto-discovers both; needed to compile against a system C library.
Structuring a Go CLI that fetches a URL
Parse args with the flag package, http.Get the URL, check err and status, defer resp.Body.Close, copy body to stdout, exit non-zero on failure.
Handling Result and errors in a Rust web handler
Handler returns Result, the ? operator early-returns errors, a custom error type implements IntoResponse to map to 500, success returns 200 with data.
In-memory rate limiter middleware in Go
Use a token-bucket limiter (golang.org/x/time/rate), guard a per-client map with sync.Mutex, wrap http.Handler so requests over the limit get 429.
Logging middleware wrapping an http.Handler in Go
Middleware has signature func(http.Handler) http.Handler, records start time, calls next.ServeHTTP, then logs method, URL, and elapsed duration; chaining works because the wrapper is itself a…
Static dispatch over Write with generics in Rust
Write generically over the std::io::Write trait with a type parameter W: Write, letting the compiler monomorphize and inline per concrete type, avoiding the vtable indirection of Box<dyn Write>.
Using context.Context across microservice calls in Go
Context carries cancellation, deadlines, and values; pass ctx as first arg, set one WithTimeout at the edge, attach a request ID via WithValue, thread it through downstream calls so all cancel…
Rust Send and Sync marker traits explained
Send means a value can move across threads, Sync means a reference can be shared; Rc uses non-atomic refcounts, Arc uses atomic ones.
Architecting an L7 proxy in Go versus Rust
Go offers GC and cheap goroutines for fast delivery but tail-latency GC pauses; Rust offers ownership and async/await for predictable latency at higher complexity.
Why Pin is needed for self-referential Futures
Async blocks compile to state machines that can hold references into their own storage; Pin guarantees the value will not move so those internal pointers stay valid across polls.
Fearless concurrency: Rust compile-time vs Go runtime
Rust uses ownership plus Send/Sync to reject data races at compile time; Go encourages channels but still allows races, with the runtime race detector catching them at test…
Rust lifetimes versus Go garbage-collected lifetimes
A lifetime is a compile-time region a reference is valid for; annotations like 'a relate input and output reference durations; Go instead uses garbage collection and escape analysis.
Criterion: the standard Rust benchmarking library
Criterion runs on stable Rust, collects many samples, applies statistical analysis with confidence intervals, and compares against saved baselines to detect regressions.
Structural Go interfaces versus nominal Rust traits
Go interfaces are satisfied implicitly by method shape (structural); Rust traits must be explicitly implemented (nominal).
Goroutines and channels versus ownership-based concurrency
Go uses cheap goroutines and CSP-style channels to coordinate by communication; Rust uses ownership plus Send/Sync to make data races a compile error.
Go (T, error) versus Rust Result for error handling
Go returns a separate error value you may ignore; Rust wraps success or error in one Result enum the compiler forces you to handle. Go favors simplicity, Rust favors compile-enforced safety.
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