Block Chain - Sequencers and Proposers

Sequencers and proposers are roles in modern blockchain and Layer-2 systems that decide the order in which transactions are processed and included in blocks. Transaction ordering is critical because it affects fairness, performance and security.

What a Sequencer Is
A sequencer is a component, commonly used in Layer-2 systems, that collects user transactions and orders them before execution. It produces blocks or batches that are later submitted to the main chain. Sequencers are designed to improve speed and user experience.

Role of Sequencers in Layer-2 Networks
In rollups and other Layer-2 solutions, the sequencer provides fast confirmations by immediately ordering transactions. Users get quick feedback instead of waiting for main-chain block times. Final security is still provided by the main blockchain.

What a Proposer Is
A proposer is a node that creates and proposes a new block to the network in a blockchain consensus system. In many protocols, proposers are selected based on staking, randomness or rotation. Their role is to package transactions into a block for validation.

Sequencer vs Proposer
Sequencers focus on transaction ordering and batching, mainly in Layer-2 systems. Proposers operate at the base-layer consensus level and are responsible for block creation. In some designs, one entity can perform both roles, while in others they are separate.

Centralization and Trust Considerations
Single sequencer designs offer speed but introduce centralization risks. If a sequencer fails or behaves maliciously, transaction ordering can be delayed or censored. Many systems are moving toward decentralized or shared sequencer models to reduce this risk.

Why Sequencers and Proposers Matter
Transaction ordering directly impacts fairness, fees and security. Understanding sequencers and proposers helps explain how modern blockchains achieve scalability while working to preserve decentralization and trust.