The Rust programming language is growing in popularity every year. It even topped StackOverflow’s Developer Survey as the most-loved programming language by those using it regularly—7 years in a row.
So, if you're an aspirant looking to get a Rust developer position, or a hiring manager looking for questions to test your candidates‘ Rust knowledge, we got you the best Rust interview questions.
Before you start
Let’s give you a quick overview of some general things before you get started. This will help you set your expectations for Rust jobs as a candidate.
- The average salary for Rust developers is $120K per annum.
- The range of Rust dev salaries starts at $60K per annum for junior developers and goes up to $140K per annum for senior developers.
- The Rust market is currently growing. This means that not only is the developer pool increasing, but the number of jobs along with it. In short: There’s plenty of market demand for Rust developers.
- Huge companies like Dropbox, Mozilla, CloudFlare, and even Discord use Rust to power their systems.
With this overview out of the way—here are your sample questions and answers:
25+ Rust Interview Questions and Answers
1. What is Rust?
Rust is a high-performance multi-purpose programming language. It is reliable and offers a rich type of system with no runtime. It provides an ownership model that makes it thread and memory safe. Its user-friendly compiler shows detailed errors for bug-free development. These make it an excellent pick for building tools, servers, and web apps.
2. What are the benefits of Rust?
There're many benefits to using Rust:
- Rust features faster execution and low-level access, similar to C and C++. But at the same time, it offers safety similar to a high-level programming language. Due to no runtime, it is ideal for high-performance-critical services and embedded solutions.
- Rust's memory-safety approach means that it lets developers write bug-free applications. It manages to prevent data races, especially when running concurrent threads.
In short, Rust enables developers to build bug-free, high-performance, and robust software.
3. Explain Rust's ownership model?
Rust manages memory through an ownership model. The model has a strict set of rules for the developer to write their programs. This leads to compile-time checks, resulting in bug-free programs. In other words, programmers must write code that takes care of memory from the onset.
The ownership rule can be summarized as follows:
- In Rust, each value has an owner.
- Only one owner at a time can be present.
- When the owner goes out of the scope, the value is dropped.
4. What is borrowing in Rust?
Borrowing in Rust is accessing variable value without taking ownership. Instead, the borrow checker carries the transaction and ensures references are valid while providing strict rules around data mutability.
A variable, once borrowed, can have its value read. Sometimes, the value can be modified depending on the access level. This simple technique allows Rust developers to write memory-safe programs devoid of common programming mistakes.
5. Can you create infinite loop in Rust? If yes, how so?
You can use the handy loop keyword to create the infinite loop.
$ rust loop {// …. }
6. How are Stack and Heap used in Rust?
Stack and Heap play a crucial role in Rust’s memory management. For optimal memory management, both must be used. However, as Heap is less organized and slower than Stack, it is best to avoid directly accessing Heap.
To circumvent the problem, the coder can use Stack to store the Heap pointer, which points to the actual heap location. This method is faster.
Also, using Stack is a better choice when using fixed-sized data types. In case of no fixed data size, Heap must be used. Also, the programmer should delete data on Heap once not required. It minimizes duplicate data to ensure the program doesn’t run out of space.
7. Why doesn't Rust use a garbage collector?
Rust doesn't use a garbage collector because memory management is done through the ownership model. A garbage collector is unnecessary as all checks are done during compile time.
However, technically, Rust has a static garbage collector that makes sure that memory that is not in use is recycled before any other program or variable tries to access it.
8. What is Cargo?
Cargo is a popular Rust package manager that lets developers manage packages and libraries. It is an excellent tool, especially when working with complex projects.
For example, it’ll take care of your Rust package’s dependencies, automatically downloading and compiling them. It is also intelligent enough to ignore build files when you use Git.
9. Which command do you use to create a new project in Rust?
You can use the cargo new command to create a new project. However, you can also approach the method manually by creating the necessary Rust files and folders. However, the cargo package manager makes Rust project handling easy and intuitive.
10. How do you use cargo to build and test Rust code?
Cargo offers plenty of commands to build and test Rust code. To create a new Rust program, use Cargo new to create a new project.
To build the project, use thr Cargo build command. And to test the project, Cargo test. It opens up the debug mode and runs the test suite.
You can run the Cargo check command to check whether the program compiles quickly. And, if you want to run and build a project together, use the Cargo run command.
11. How you convert a normal Rust program to Cargo compatible?
Changing a non-cargo project to Cargo requires you to do two steps:
- Move your main.rs file to the src directory
- And create a Cargo.toml file.
In the Cargo.toml file, you want to add the necessary structure, which includes [package] and [dependencies].
The default code for Cargo.toml is:
[package]
name = “guessing_game”
version = “0.1.0”
edition = “2021”
# See more keys and their definitions in the Rust Documentation
[dependencies]
12. What is Rust Reference &?
The & symbol creates a reference to a value. Once created, the value is borrowed.
fn main() {
let x = 5;
let y = &x;
println!("{}", y);
}13. What is Rust Macro? And how it is different from a function?
Rust offers macros like println! It refers to a set of features in Rust.
Technically, macros deal with metaprogramming, where a set of code/way of writing code generates other code. It helps reduce the amount of code which in return reduces code maintenance.
A macro differs from a function in how they are declared and executed. In Rust functions, it is essential to declare the type and number of parameters. Macros don’t require this approach and can take one or more parameters.
Another big difference is that macros are expanded before the compiler intercepts them, which is invalid for Rust functions.
14. Tell us about the rustfmt automatic formatter tool
rustfmt is a useful Rust development tool with automatic formatting based on the community code style.
This improves collaboration and prevents any issues related to code style. So, if the team uses rustfmt, everyone follows the same style.
To add rustfmt to the project, run the following command:
$ rustup component add rustfmt
15. Explain error handling in Rust.
Error handling in Rust works differently compared to other programming languages. Here, Rust doesn’t use exceptions but instead breaks the errors into two categories: recoverable and unrecoverable.
Recoverable errors are errors that can be solved or are primarily user based. For example, file not found error. In case of recoverable errors, the program doesn’t stop and asks for a retry from the user.
In case of an unrecoverable error, Rust initiates its panic macro. It prints the message, unwinds, cleans the stack, and quits. Examples of unrecoverable errors include accessing an array beyond its length.
16. Is Rust ready for web?
Rust is ready for the web if you consider production-ready frameworks such as Axum and Actix Web. On top of that, other popular Rust web frameworks like Warp and Tide exist.
These frameworks are complete web solutions and give developers access to essential tools, including templating, routing, middleware, and form handling. And you have crates and databases such as SQLx and Diesel.
Rust for the web can be a game changer considering that developers can take advantage of WebAssembly.
17. What are common data type in Rust?
Rust common data types include integers, booleans, floating-point numbers, and characters.
18. What is the purpose of the mut keyword in Rust?
In Rust, variables are immutable. This safety-first approach makes Rust bug-free and offers excellent concurrency. The mut keyword tells the Rust compiler that the variable is now mutable.
let mut guess = String::new()
In the above code, a mutable guess variable is created. It is also bound to an empty String instance.
19. Does Rust have any disadvantages? If it does, mention them.
Rust does have some disadvantages, similar to any other programming language. These disadvantages include:
- Rust compilation takes time to complete
- Rust's borrowing system is complicated.
- Rust has a higher learning curve, which could be a challenge in situations where the team needs to learn Rust in a timely manner for an upcoming project.
- Rust is still new, which means that many of its libraries are not yet complete
20. How you declare global variable in Rust?
To declare a global variable in Rust, use the const keyword. You can also use the static keyword to declare a global variable which gives the mutable variable status. However, it is not recommended to use static as it is an unsafe practice.
21. What purpose does Cargo.lock file offer?
The Cargo.lock file keeps a tab on all application dependencies.
22. Can operating systems be written in Rust?
Rust is a multi-purpose programming language. It is equipped with all the low-level access features and hence offers appropriate features to write a complete operating system. For example, Redox and Google’s KataOS are written in Rust.
23. What is the difference between emum and struct in Rust?
A struct in Rust is a data type you can use to create your custom data type. It is helpful to encapsulate data and then access it later on. For example, in a struct, you can create multiple fields where each field can have its data type.
Below is the example:
struct Omega {
x: i32,
y: i32,
z: "string"
}
fn main() {
let p = Omega { x: 1, y: 2, z: "hello" };
println!("{} {} {}", p.x, p.y, p.z);
}
#output
1 2 hello
```
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<p><strong>Enum, </strong>on the other hand, lets you create a type with different variants.</p>
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<pre class="wp-block-code"><code># enum example in Rust
```rust
// Language: rust
enum Direction {
Up,
Down,
Left,
Right
}
24. Provide impl block example in Rust.
An impl block in Rust lets you implement Rust’s struct and enum data types.
# example of impl block in Rust
impl Direction {
fn as_str(&self) -> &'static str {
match *self {
Direction::Up => "up",
Direction::Down => "down",
Direction::Left => "left",
Direction::Right => "right",
}
}
}
25. Write an example of a generic Rust function
Rust trait lets programmers define shared behavior for shared types. It can hold more than one method for an unknown type Self.
trait Animal {
fn new(name: &'static str) -> Self;
fn name(&self) -> &'static str;
fn talk(&self) {
println!("{} cannot talk", self.name());
}
}
26. What can you create with Rust?
Rust is a general-purpose language. You can use it in domains like web servers, databases, operating systems, and real-time and secure applications.
Candidate-specific questions
In any interview, the interviewer asks questions you have to answer by filling in your own experience. These questions can include
- Tell us about your Rust projects.
- Please walk us through the architecture of one of your Rust projects.
- What is the most challenging task you did related to Rust? And how did you manage to overcome it?
You can practice answering these questions beforehand so that you’ll be able to handle them with confidence.
Overall, Rust programming is relatively new. If you’re applying for a beginner-level Rust job, your questions will mostly cover beginner stuff. For experienced developers changing their careers, most questions would be advanced or Rust project specific.