Question 1

What is Proposer-Builder Separation (PBS)?

Accepted Answer

PBS separates the roles of block proposing and block building in Ethereum. Validators (proposers) no longer need to construct blocks themselves - specialized builders compete to create the most profitable block, and proposers simply select the highest bid. This reduces centralization pressure on validators.

Question 2

What is MEV-Boost?

Accepted Answer

MEV-Boost is middleware developed by Flashbots that implements PBS out-of-protocol. Validators run MEV-Boost alongside their consensus client to receive blocks from a competitive builder market via trusted relays, earning higher rewards than building blocks locally.

Question 3

What is enshrined PBS (ePBS)?

Accepted Answer

Enshrined PBS (ePBS) moves proposer-builder separation into the Ethereum protocol itself, removing the need for trusted relays and external middleware like MEV-Boost. It's part of Ethereum's long-term roadmap to make PBS a native protocol feature.

Question 4

Why does builder concentration matter?

Accepted Answer

If a few builders dominate block production, they gain outsized power to censor transactions or extract MEV. High builder concentration undermines Ethereum's censorship resistance, which is why research into ePBS and inclusion lists is critical.

Feature	MEV-Boost	ePBS
Trust model	Trusted relays	Trustless
Implementation	Out-of-protocol	In-protocol
Censorship resistance	Relay-dependent	Inclusion lists
Latency	~200ms relay overhead	Protocol-native
Status	Live since 2022	Research / EIPs

Proposer-Builder Separation

MEV-Boost Block Flow

Block Building Simulator

Builder Market Share

Relay Trust Model

MEV-Boost vs ePBS

PBS Stats Dashboard