Here’s a comprehensive list of Solana Anchor Framework interview questions, ranging from beginner to expert, covering coding, technical concepts, and best practices.
Table of Contents
Solana Anchor Framework Beginner Level Questions
1. What is Solana, and how does it differ from Ethereum?
- Answer: Solana is a high-performance blockchain with low fees and high transaction throughput. Unlike Ethereum, which relies on Proof-of-Stake and Proof-of-Work (before ETH 2.0), Solana uses Proof-of-History (PoH) combined with Proof-of-Stake (PoS) to achieve fast consensus.
2. What is the Anchor framework?
- Answer: Anchor is a Rust-based framework for building Solana smart contracts. It simplifies program development with macros, automatic serialization, and security features.
3. How do you initialize a new Anchor project?
anchor init my_project
cd my_project
This sets up the project with the default directory structure.
4. What is the structure of an Anchor program?
programs/: Contains Rust smart contracts.tests/: Includes JavaScript/TypeScript-based test scripts.migrations/: Deployment scripts.anchor.toml: Configuration file.
5. What are PDA (Program Derived Addresses) in Solana?
- Answer: PDAs are deterministic addresses derived from a program’s public key + seeds, making them program-controlled accounts.
6. How do you derive a PDA in Anchor?
#[account(
seeds = [b"user", user.key().as_ref()],
bump
)]
pub user_account: Account<'info, User>;
Uses seeds to derive the PDA.
7. What is the purpose of the ctx parameter in an Anchor instruction?
- Answer:
ctxprovides context, containing accounts, signers, and remaining accounts needed for a transaction.
8. What are the types of Solana accounts in Anchor?
- Answer:
- System Accounts: Basic wallet addresses.
- Program Accounts: Stores data related to the program.
- PDAs: Controlled by smart contracts.
9. How do you define a struct for a user in Anchor?
#[account]
pub struct User {
pub authority: Pubkey,
pub balance: u64,
}
This struct is stored in a program account.
10. How do you serialize and deserialize data in Anchor?
- Answer: Anchor automatically serializes/deserializes accounts using Borsh.
Solana Anchor Framework Intermediate Level Questions
11. How do you define an instruction in Anchor?
pub fn create_account(ctx: Context<CreateAccount>, balance: u64) -> Result<()> {
let user = &mut ctx.accounts.user_account;
user.authority = *ctx.accounts.authority.key;
user.balance = balance;
Ok(())
}
Defines a function to create an account with an initial balance.
12. What is the difference between Program Account and System Account?
- System Account: Default Solana wallet account.
- Program Account: Holds custom structured data for smart contracts.
13. What is the purpose of bump in PDA?
- Answer:
bumpis the last byte added to avoid collisions.
14. How do you handle signer verification in Anchor?
#[derive(Accounts)]
pub struct CreateAccount<'info> {
#[account(mut, signer)]
pub authority: Signer<'info>,
}
The Signer macro ensures the authority signed the transaction.
15. What is the maximum account size in Solana?
- Answer: 10MB, but most accounts are smaller due to rent costs.
16. What is the function of invoke_signed in Solana?
- Answer: Calls another Solana program with signatures.
invoke_signed(
&instruction,
&[ctx.accounts.user.to_account_info()],
&[&["user".as_bytes(), &[bump]]]
)?;
17. How do you transfer SOL between accounts in Anchor?
let ix = anchor_lang::solana_program::system_instruction::transfer(
&ctx.accounts.from.key(),
&ctx.accounts.to.key(),
amount,
);
anchor_lang::solana_program::program::invoke(
&ix,
&[ctx.accounts.from.to_account_info(), ctx.accounts.to.to_account_info()]
)?;
Uses system_instruction::transfer.
18. How do you store data in a PDA?
#[account(
init,
payer = user,
space = 8 + 32 + 8,
seeds = [b"user", user.key().as_ref()],
bump
)]
pub user_account: Account<'info, User>;
space = 8 + 32 + 8 allocates space.
19. How do you implement a staking smart contract in Anchor?
- Answer: A staking contract should:
- Accept deposits.
- Track staking duration.
- Reward users for staking.
Solana Anchor Framework Advanced Level Questions
20. How do you optimize Solana smart contracts?
- Minimize account data.
- Use PDAs instead of storing pubkeys.
- Use compression techniques.
21. What is the SystemProgram account in Solana?
- Answer: Solana’s built-in program for account creation, funding, and transfers.
22. How do you prevent reentrancy attacks in Anchor?
- Answer: Use checks-effects-interactions.
pub fn withdraw(ctx: Context<Withdraw>, amount: u64) -> Result<()> {
let user = &mut ctx.accounts.user_account;
require!(user.balance >= amount, CustomError::InsufficientFunds);
user.balance -= amount;
invoke_signed(...) // Transfer SOL
}
Ensures state updates before transfers.
23. How does Anchor handle CPI (Cross-Program Invocation)?
- Answer: It uses
invoke_signedto call external programs.
24. How do you add error handling in Anchor?
#[error_code]
pub enum CustomError {
#[msg("Insufficient funds")]
InsufficientFunds,
}
Custom errors improve debugging.
25. How do you test an Anchor program?
const program = anchor.workspace.MyProgram;
await program.rpc.createAccount({ accounts: { user: user.publicKey } });
Uses Anchor’s Mocha-based testing framework.
Solana Anchor Framework Expert-Level
26. Explain Rent Exemption in Solana.
Solana requires accounts to maintain a minimum balance to be rent-exempt. This ensures they remain on-chain permanently. The rent-exempt balance depends on the account’s size and is calculated as:
minimum_balance = 0.00289088 SOL per byte * account_size
If an account falls below this threshold, it may be deleted, and any remaining SOL is reclaimed.
How to Check for Rent Exemption
let rent = Rent::get()?.minimum_balance(account_size);
27. What is Zero-Copy Storage?
Zero-Copy Storage is a way to store data without serialization, using memory-mapped data structures. Instead of converting data to/from byte arrays (as in Borsh), it uses direct memory access, reducing overhead.
Example Using Zero-Copy in Anchor
#[zero_copy]
pub struct MyStruct {
pub owner: Pubkey,
pub amount: u64,
}
28. How does Anchor handle account security?
Anchor automatically checks account ownership, seeds, and permissions through:
#[account(mut)]: Ensures the account is mutable.has_one = owner: Validates the account owner.- PDAs (Program Derived Addresses): Prevents unauthorized access.
29. How do you write upgradeable smart contracts in Solana?
Use Solana Program Deployment (BPF Upgradeable Loader):
- Deploy an initial program.
- Store the upgrade authority in a separate account.
- Use
solana program deploy --upgrade-authority <KEYPAIR>.
30. Explain Compute Budget Optimization in Solana.
Solana limits compute units per transaction (~200,000 units). Optimizations include:
- Minimizing account access.
- Using efficient data structures (e.g., Zero-Copy).
- Parallelizing transactions with Sealevel.
31. What is getProgramAccounts()?
A Solana RPC method to fetch all accounts owned by a specific program:
const accounts = await connection.getProgramAccounts(programId);
Useful for indexing and querying NFTs, token balances, or DeFi positions.
32. How do you deploy a program on Solana Mainnet?
- Set up Solana CLI:
solana config set --url mainnet-beta - Deploy using Anchor:
anchor build anchor deploy
33. What are Feature Gates in Solana?
Feature Gates allow Solana to enable/disable features without a hard fork. Example: Compute budget increases, new opcodes.
34. Explain Serde vs. Borsh.
- Serde: More flexible but slower (used in JSON serialization).
- Borsh: Faster, smaller, and designed for Web3 (used in Anchor & Solana).
35. How do you implement NFT minting in Anchor?
Use Metaplex Token Metadata Program:
let mint_ix = spl_token::instruction::mint_to(
&spl_token::ID, &mint_account, &receiver, &authority, &[&authority], 1
);
36. How does Solana prevent front-running?
Solana has atomic transactions and block scheduling, reducing MEV (Miner Extractable Value).
37. How does Solana handle sharding?
Solana does not use traditional sharding but relies on Sealevel parallel execution and multiple leader schedules.
38. What are Priority Fees in Solana?
Users can increase fees to prioritize their transactions when network congestion occurs.
solana transfer <wallet> <amount> --priority-fee 10000
39. How do you debug a Solana transaction?
Use:
solana logs
solana transaction-history <tx_signature>
40. How do you implement a Decentralized Exchange (DEX) in Anchor?
Use the Serum DEX or Raydium protocols with CPI (Cross-Program Invocation).
invoke_signed(&serum_dex_instruction, &[account_infos], &[seeds]);
41. Explain Solana State Compression.
Solana compresses large datasets (NFT metadata, Merkle trees) to reduce on-chain storage costs.
42. What is Metaplex?
Metaplex is Solana’s NFT standard, providing:
- NFT Metadata.
- On-chain royalties.
- Candy Machine for minting collections.
43. Explain Oracles in Solana.
Oracles provide real-world data to smart contracts (e.g., price feeds). Example: Pyth Network, Switchboard.
44. What is Geyser Plugin?
A real-time data streaming tool that allows Solana programs to push blockchain data to external databases.
45. How do you handle multi-signature wallets?
Use Solana’s Multisig program or SafeSnap (Gnosis Safe for Solana).
invoke_signed(&multisig_instruction, &[signers], &[seeds]);
46. What is Switchboard Oracle?
A decentralized oracle network on Solana, similar to Chainlink, but optimized for fast price feeds
47. Explain Flash Loans in Solana.
Flash Loans allow borrowing without collateral as long as the loan is repaid within the same transaction.
invoke_signed(&flash_loan_ix, &[accounts], &[seeds]);
48. How does Solana implement Wormhole Bridging?
Wormhole is a cross-chain messaging protocol for asset bridging across Ethereum, BSC, Solana, Terra.
49. How does Triton VM impact Solana?
Triton VM is a Solana-compatible zkVM (Zero-Knowledge Virtual Machine), improving privacy and scalability.
50. What’s next for Solana?
- Firedancer Validator (Jump Crypto’s parallel validator).
- More efficient fee markets (dynamic priority fees).
- Expansion into Web3 gaming and AI integration.
