How to Build an Intent-Based DEX Aggregator With Solver and Filler Networks

The frontend should allow users to specify:

• Token to sell
• Minimum token output
• Chain
• Recipient
• Deadline
• Slippage or price constraints
• Optional gas preferences
• Optional routing preferences

The resulting order should be cryptographically signed using standards such as EIP-712 where appropriate.

The important design principle is that the user signs constraints, not an execution path.

That prevents the frontend from locking users into a predetermined DEX route.

2. Intent Mempool and Orderbook

Signed intents should enter an off-chain orderbook or auction service.

The orderbook needs to validate:

• Signature
• Nonce
• Token balances
• Allowances or permits
• Expiration
• Chain ID
• Reactor/settlement contract
• Minimum output
• Order status

This layer should also prevent duplicate fills and expired-order execution.

CoW Protocol's architecture similarly separates the orderbook from its auction orchestration layer, with the orderbook handling quotes, orders, cancellations, and auction state.

3. Solver Network