Solana PDAs Explained: How Stateless Programs Store User Data On-Chain

Solana programs are stateless, so they rely on Program Derived Addresses (PDAs) to deterministically locate user-specific data without storing addresses explicitly. PDAs function similarly to database primary keys in Web2, but are derived on demand using a hash of seed values and the program ID, ensuring only the owning program can sign for them. The choice of seeds is critical: including a user's public key in the seeds generates a unique PDA per wallet, while omitting it produces a single shared address suitable for global configuration. A 'bump' byte is used to push the derived address off the elliptic curve, and storing it on the account avoids costly re-derivation on subsequent instructions. The full PDA lifecycle covers four stages: deriving the address, initializing the account, mutating its data, and eventually closing it.