Signed Extensions

SignedExtension in sp_runtime::traits - Rust

Substrate provides the concept of signed extensions to extend an extrinsic with additional data, provided by the SignedExtension trait.

The transaction queue regularly calls signed extensions to keep checking that a transaction is valid before it gets put in the ready queue. This is a useful safeguard for verifying that transactions won't fail in a block. They are commonly used to enforce validation logic to protect the transaction pool from spam and replay attacks.

Reference

pallet-transaction-payment 38.0.0 - Docs.rs