Solidity Solidity Advanced Patterns and Architecture

Question 1

What is the purpose of the Proxy Upgrade Pattern (UUPS or Transparent Proxy) in Solidity?

Accepted Answer

It allows replacing a contract's logic while preserving its storage state and address

Answer

It allows a contract to pay its own gas fees

Answer

It enables a contract to call itself recursively without a stack limit

Answer

It provides automatic circuit-breaker functionality

Question 2

What is the key difference between UUPS and Transparent Proxy upgrade patterns?

Accepted Answer

UUPS places upgrade logic in the implementation contract; Transparent Proxy places it in the proxy contract

Answer

UUPS uses delegatecall while Transparent Proxy uses staticcall

Answer

Transparent Proxy supports ERC-20 while UUPS does not

Answer

UUPS requires a multisig while Transparent Proxy does not

Question 3

What is the Factory pattern in Solidity and what problem does it solve?

Accepted Answer

A contract that deploys other contracts programmatically, enabling on-chain contract creation with tracked addresses

Answer

A pattern that caches expensive computations across multiple calls

Answer

A pattern that batches multiple ERC-20 transfers into one transaction

Answer

A contract that generates random salt values for CREATE2 deployments

Question 4

What does `CREATE2` opcode allow that `CREATE` does not?

Accepted Answer

Deterministic contract address calculation before deployment, based on deployer + salt + bytecode hash

Answer

Deploying contracts without a constructor

Answer

Deploying contracts that can be self-destructed and redeployed

Answer

Deploying to a different chain with the same address automatically

Question 5

What is the Diamond Pattern (EIP-2535) in Solidity?

Accepted Answer

A proxy pattern that routes function calls to multiple implementation contracts (facets) based on function selectors

Answer

A multi-sig pattern where approvals form a diamond graph

Answer

A storage pattern using diamond inheritance for cheaper reads

Answer

A token standard combining ERC-20 and ERC-721 in one contract

Question 6

What is the purpose of the `initializer` modifier in OpenZeppelin's upgradeable contracts?

Accepted Answer

It ensures the initialization function can only be called once, replacing the constructor for proxy-based contracts

Answer

It marks a function as payable during deployment only

Answer

It automatically calls the parent contract's constructor

Answer

It prevents the contract from being paused during initialization