With the introduction of ERC-4337, the Ethereum ecosystem has taken a major step towards enhancing the Web3 user experience through Account Abstraction. This approach, which aims to simplify interactions with the blockchain, introduced new entities called bundlers. A bundler is designed to collect multiple user operations (UserOps) into a single transaction and submit it to the blockchain, which enables AA capabilities.

A collaborative effort for decentralization

One of the core purposes of bundlers is decentralization. Bundlers provide access to a smart account without depending on centralized relayers controlled by a single entity. To support bundlers' operation and maintain the open, decentralized nature of blockchain technology, the Shared Mempool was developed. It was a collaborative effort between the Etherspot, ERC-4337, Alchemy, Candide, and Silius teams. The key role of the Shared Mempool is to ensure that userops from one bundler are shared across all of its connected peers.

The first Shared Mempool was launched on Ethereum’s testnets earlier this year. Today we are thrilled to announce its launch on Ethereum, Arbitrum and Optimism.

A development from FastLane Labs, known as PFL, played an important role in enabling Shared Mempool support on Polygon. This advancement allows ERC-4337 bundlers to submit bundles with userops to Polygon validators without passing on the costs of reverted transactions to users if frontrunning occurs. The work by FastLane Labs means that the Shared Mempool will soon be available on Polygon as well.

What is the concept behind the Shared Mempool?

When a user initiates a user operation via a smart account, this user operation is validated by a bundler and then shared with all peer bundlers via a peer-to-peer network. If one bundler is unable to process the operation, other bundlers on the network can take over, ensuring the operation is completed.

This decentralized approach, which mimics the standard Ethereum mempool, improves the reliability and efficiency of the network by preventing delays or congestion that could occur if one bundler were responsible for processing the operation. It also ensures that users are not dependent on a single point of failure, helping maintain the openness, censorship-resistance and resilience of the network.

Connecting an ERC-4337 bundler to the Shared Mempool

The rollout of the Shared Mempool is being carried out in a phased manner, as outlined here.

Launching a truly public and decentralized mempool for ERC-4337 is a complex process, and development will progress with “training wheels” — a controlled setup that allows for system updates and bug fixes in a safer environment. While necessary in the early stages, these training wheels will be gradually removed, enabling Bundlers to fully adopt the decentralized principles of the base layer.

By enabling a decentralized, efficient process for managing userops, the Shared Mempool represents a crucial step forward in Account Abstraction. This development contributes to the long-term sustainability and scalability of the Ethereum ecosystem.

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