The division between data and logic that live in the blockchain, where they are public, permanent, and expensive, and everything kept in ordinary systems, where it is cheap, fast, and changeable.
This split is the central architectural decision in any Web3 product. Putting too much on-chain makes it slow and costly; putting too little leaves nothing that actually benefits from decentralisation.
We keep ownership, settlement, and anything that must be trustless on-chain, and keep search, history, personal data, and interface state off-chain, with indexers that make on-chain data fast to read.