Here’s a fresh take on the Move Programming Interview Questions with Answers, crafted to feel warm, approachable, and human while staying sharp and accurate. I’ve organized it by difficulty level to guide developers prepping for interviews about the Move language, which powers blockchains like Aptos and Sui. Think of this as your friendly study buddy, ready to help you nail those technical questions with confidence!
1. So, what exactly is the Move programming language, and where’s it popping up these days?
Answer:
Move is a smart contract language cooked up by Meta (back when it was Facebook) for their Diem blockchain. Today, it’s the go-to language for blockchains like Aptos and Sui. It’s all about safety and precision, especially for handling digital assets like tokens, thanks to its clever resource-focused system that prevents stuff from getting duplicated or lost by mistake.
2. Why is Move such a great pick for blockchain projects?
Answer:
Move’s got some killer features that make it a blockchain superstar:
- Resource types: Keeps assets like tokens safe and sound.
- Strong typing: Spots errors before your code even runs.
- Abilities: Lets you control exactly how data can be used.
- Predictable execution: No weird surprises when contracts run.
- Formal verification: With tools like Move Prover, you can prove your code’s rock-solid.
3. What’s the deal with resources in Move?
Answer:
Resources are Move’s way of handling valuable things like tokens or NFTs. Unlike regular data, you can’t accidentally copy or toss them out. The Move virtual machine (VM) makes sure each resource lives in just one spot at a time, which is perfect for keeping ownership clear and transfers secure.
4. How does Move lock down resources and decide who gets to touch them?
Answer:
Move uses a special signer type to check who’s behind a transaction, ensuring only the resource’s owner can mess with it. On top of that, its resource system stops resources from being copied or deleted by accident, keeping everything tightly secured.
5. What’s the difference between a struct and a resource struct in Move?
Answer:
- A struct is your everyday data type—copy it, drop it, no big deal. It’s like a casual notebook you can scribble in.
- A resource struct is way stricter. It follows Move’s “no copy, no drop” rules, making it ideal for serious stuff like coins or collectibles that need to stay unique and protected.
6. How do you share a Move module with the world?
Answer:
You write your module in a .move file, then use a blockchain’s CLI (like Aptos or Sui’s) or SDK to publish it. The account you use to publish sets the module’s address, which is like its permanent home on the blockchain. It’s your way of saying, “Here’s my code, ready for action!”
7. What’s up with the signer type in Move?
Answer:
The signer is like a digital badge that shows who’s sending a transaction. It lets your smart contract know who’s trying to do something—like moving tokens or updating data—so only the right person can make changes.
8. How does Move compare to Solidity?
Answer:
Move and Solidity are both smart contract languages, but they’re like apples and oranges. Move’s resource-focused design stops asset duplication or loss right in the code, while Solidity depends on runtime checks and careful coding to stay safe. Move also comes with built-in formal verification via the Move Prover, while Solidity needs external tools like MythX or Slither. Move’s stricter and safer; Solidity’s more flexible but trickier to get right.
9. What are abilities in Move, and how do you work with them?
Answer:
Abilities are like rules for Move types, deciding what you can do with them. There are four: copy, drop, store, and key. For example, key lets a struct live on-chain, and copy allows duplication. You set these when defining a struct to make sure it behaves just the way you want, giving you total control.
10. What’s the has keyword doing in Move?
Answer:
The has keyword tells Move which abilities a struct gets when you define it. Like, struct Coin has key, store says the Coin can be stored on-chain (key) and nested in other structs (store). It’s your way of setting the ground rules for how that type works.
11. How does Move keep resources safe and sound?
Answer:
Move’s linear type system is the magic here. It makes sure resources can’t be copied or thrown out unless you explicitly say so. The compiler checks that every resource gets moved, stored, or destroyed properly by the end of a transaction, so you don’t end up with issues like double-spending or lost assets.
12. What are module addresses, and why should I care?
Answer:
Module addresses are like the GPS coordinates for a Move module on the blockchain. They’re set when you publish the module and used to import or call its functions. They keep modules unique and help enforce who owns what, making sure everything stays organized and secure.
13. How would you build a simple token contract in Move?
Answer:
You’d start with a resource struct Token to hold details like amount or metadata. Then, add public entry functions for the big moves: mint to create tokens, transfer to send them between accounts, and burn to get rid of them. Use the signer to make sure only authorized folks can mint or burn, keeping your contract locked down.
14. How do generics fit into Move modules?
Answer:
Generics are Move’s way of letting you write reusable, flexible code. For example, you could create a Vault<T> struct to store any kind of token, as long as T plays by certain rules (like having the store ability). Generics keep your code clean, type-safe, and ready to handle different types without repeating yourself.
15. What’s a Script in Move, and how’s it different from a Module?
Answer:
- A Script is a one-shot deal—a single transaction you send to the blockchain to do something specific. It runs once and vanishes.
- A Module is like a permanent toolbox, packed with reusable code (structs, functions, constants) that lives on-chain and can be called by scripts or other modules. Scripts are for doing; modules are for building.
16. How does Move deal with concurrency and parallel execution?
Answer:
Move’s VM is pretty smart about concurrency. It checks transactions to see which ones touch the same resources. If two transactions don’t overlap, they can run side by side, speeding things up. This clever analysis keeps everything predictable while making the blockchain run faster.
17. What’s the Move Prover, and how does it make smart contracts bulletproof?
Answer:
The Move Prover is a formal verification tool that lets you prove your Move code is correct, like a math teacher checking your work. You write specs (using Move’s spec language) to say what your code should do—like keeping resources safe or maintaining key rules. The Prover double-checks these, catching sneaky bugs before they hit the blockchain.
18. How do you stop reentrancy attacks in Move?
Answer:
Move’s resource model is a natural defense against reentrancy, since it blocks shared mutable state and prevents resource copying. To stay extra safe, avoid nested external calls and keep access patterns clear. Move’s strict rules make reentrancy attacks way tougher than in other languages.
19. What’s the lifecycle of a transaction in Aptos or Sui using Move?
Answer:
Here’s the journey:
- A user signs a transaction, often calling a Move entry function.
- Validators on the blockchain verify the signature and run the transaction in a safe, sandboxed Move VM.
- If it’s all good, the VM updates the blockchain’s state—like moving resources or saving data.
- The user gets a result back, like “success!” or an error message.
20. Can you upgrade contracts in Move, or is that off the table?
Answer:
Move doesn’t let you tweak modules after they’re published—they’re locked in for good. This immutability keeps contracts predictable and trustworthy. To “upgrade,” you publish a new module at a fresh address or version and move the state over. It’s a intentional choice to prioritize stability and security.
21. How would you create a decentralized app (dApp) with Move modules?
Answer:
You’d kick things off by writing Move modules to handle the core logic and data—think token transfers, user profiles, or game rules. These modules hold reusable structs and functions. Then, build a front-end (like a web or mobile app) or use CLI tools to talk to the modules, sending transactions to trigger their functions. Add smart contract patterns like access control and secure storage, and you’ve got a solid dApp ready to roll.
22. Can you explain how Move’s storage model works?
Answer:
In Move, every account gets its own private storage space. Only types with the key ability can be stored directly under an account’s address. To change storage, you use specific functions like move_to to save a resource or move_from to pull one out. This clear, explicit approach keeps state changes transparent and secure.
