Key Solidity Patterns That Cut Gas Costs and Prevent Smart Contract Exploits

A developer writing for DEV Community has outlined practical Solidity patterns drawn from real-world experience, including a costly NFT minting contract that charged users $180 more per transaction than estimated due to poor storage layout. The guide explains that Ethereum storage operations are far more expensive than computation, with writing a new 32-byte slot costing 20,000 gas compared to just 5,000 for updating an existing one. Declaring state variables in the correct order allows Solidity to pack multiple smaller types into shared slots, significantly reducing a contract's storage footprint. The article also covers the checks-effects-interactions pattern, which prevents reentrancy attacks by requiring that state be updated before any external contract calls are made. The patterns are framed around two priorities: ensuring correctness under adversarial conditions and minimising gas costs per operation.