Rent and Account Creation

Every Solana account must hold a minimum SOL balance (~0.00089 SOL for basic accounts) to be rent-exempt — accounts below this get deleted
Sending SOL to a new address that has never received anything will fail if the amount doesn't cover rent-exempt minimum
Token accounts require separate rent deposits — each new token type a wallet holds costs ~0.002 SOL to create
Close unused token accounts to recover rent: spl-token close returns the SOL to owner

Token Accounts (SPL Tokens)

Unlike Ethereum, Solana wallets don't automatically hold tokens — each token needs an Associated Token Account (ATA) created first
First-time token transfers must create the recipient's ATA — sender pays ~0.002 SOL account creation fee
"Account not found" error usually means the ATA doesn't exist yet, not that the wallet is invalid
One wallet can have multiple ATAs for the same token (non-associated) — always use the ATA address for standard transfers

Base fee is ~0.000005 SOL (5000 lamports) per signature — much cheaper than Ethereum
Priority fee = compute units × price in micro-lamports — set via SetComputeUnitPrice instruction
During congestion (NFT mints, popular DEX), transactions without priority fees get dropped, not queued
Default compute unit limit is 200k per instruction — complex programs may need SetComputeUnitLimit to increase