You know the stats. Rust and Go are the money languages. Java pays $160k. Go pays $220k. Rust pays $300k (in HFT). But the interviews are brutal. They won't ask you to reverse a string. They will ask you about memory models, garbage collection latencies, and concurrency primitives. Here is how to survive the interview for the highest-paying backend roles.
For more on technical interviews, check out our guide on technical debt questions.
The Scenario
Interviewer: "Design a Rate Limiter." Junior Answer: "I'd use Redis." Senior Answer: "It depends. Are we optimizing for throughput (Go) or latency (Rust)? If we need to handle 10M requests/sec with zero GC pauses, I'd use Rust with atomic counters. If we need to ship it in 2 days and onboard 5 juniors, I'd use Go." The Result: The Senior gets the offer.
The Old Way vs. The New Way
The old way was "Algorithms." The new way is "Systems."
| Feature | Java / Python (Old Guard) | Rust / Go (New Guard) |
|---|---|---|
| Focus | OOP Patterns. | Memory & Concurrency. |
| Question | "Explain Polymorphism." | "Explain the M:N Scheduler." |
| Performance | "Good Enough." | "Cycle-Perfect." |
| Pay Ceiling | ~$200k. | ~$400k+. |
1. The "Philosophy" Trap
Q: "Should we use Rust or Go for this microservice?"
- The Trap: Being a fanboy. "Rust is always better!"
- The Answer: "Developer Velocity vs. Execution Velocity."
- Go: Use for IO-bound services (APIs, CRUD). It's fast to write, easy to read, and handles concurrency well.
- Rust: Use for CPU-bound services (Crypto, Video Encoding, Real-Time Analytics). It has no GC pauses and guarantees memory safety.
2. The Golang Deep Dive
Q: "How is a Goroutine different from a System Thread?"
- The Answer: The M:N Scheduler.
- System Threads: Expensive (~1MB stack). Context switching requires a syscall.
- Goroutines: Cheap (~2KB stack). Managed by the Go Runtime (User Space). The runtime multiplexes thousands of Goroutines onto a few OS threads.
Q: "How does the Go Garbage Collector work?"
- The Answer: Tricolor Mark-and-Sweep. It trades throughput for latency. It runs frequently to keep pauses short (sub-millisecond), but it burns CPU cycles to do so.
3. The Rust Deep Dive
Q: "Explain Ownership to a 5-year-old."
- The Answer: "Only one person can hold the toy at a time. If I give it to you, I can't play with it anymore unless I ask to 'borrow' it."
- Technical: Values have a single owner. When the owner goes out of scope, the value is dropped. No GC needed.
Q: "Why Arc<Mutex<T>>?"
- The Answer: Thread Safety.
Rc: Reference Counted (Not thread-safe).Arc: Atomic Reference Counted (Thread-safe).Mutex: Ensures only one thread can access the data at a time.
The Real Numbers
Where is the money?
| Role | Language | Base Salary (Est) | Industry |
|---|---|---|---|
| Backend Engineer | Java / Python | $160k | Enterprise |
| Cloud Engineer | Go | $220k | SaaS / Cloud |
| Systems Engineer | Rust | $280k+ | HFT / Crypto / AI |
Frequently Asked Questions
Q: Is Rust too hard to learn? A: Yes, the learning curve is steep. But that's why it pays more. It's a barrier to entry.
Q: Can I learn both? A: Yes, but pick one to master first. Go is easier to pick up in a weekend. Rust takes months.
Q: Do startups use Rust? A: Rarely. It slows down development too much. Startups use Go or TypeScript. Rust is for mature, high-scale problems.
Q: What about C++? A: C++ pays well (HFT), but it's "unsafe." Rust is eating C++'s lunch because it offers the same speed without the memory bugs.