Rundler

Why it's ranked here

Rundler is a serious infrastructure choice because its architecture addresses validation, reorg handling, profitability, signing, submission, and transaction replacement as one system. Alchemy uses it for its own account-abstraction APIs. The warning is equally serious: interfaces may break, documentation remains unfinished, and production use is explicitly at the operator's risk.

What's good

The modular deployment model is unusually practical. Stateless RPC and builder services can scale separately from stateful components, while an integrated node keeps smaller deployments simple. The pool rechecks protocol rules, tracks entity reputation, and restores cached operations after supported chain reorgs. The builder re-simulates candidates, filters for profitability, coordinates workers, and supports private keys, mnemonics, or AWS KMS signing.

Tradeoffs

Operators must build the Docker image themselves because no prebuilt image is provided. Local operation requires an EVM RPC endpoint supporting trace calls, plus a private key or another signer setup. Distributed AWS KMS signing also requires Redis for key leasing. Documentation disagrees on Entry Point coverage: the overview lists two versions, while CLI configuration exposes four.

How to use it well

Choose Rundler when operating account-abstraction infrastructure and when control over mempool policy, fee rules, signers, transaction submission, or horizontal scaling matters. Start with the integrated node, then split RPC, pool, and builder services when operational load justifies it. It does not replace the upstream EVM node or provide a hosted API by itself.

Observed

Primary language

Rust, using a Cargo workspace and Rust 2024 edition.

Licensing

Library code uses LGPL-3.0; binary code uses GPL-3.0; the repository also states Unicode License v3.0 coverage.

Install surface

Source build through Cargo or a locally built Docker image; no prebuilt Docker image is provided.

Interfaces

Command-line binary, HTTP JSON-RPC API, health endpoint, metrics endpoint, and internal gRPC service interfaces.

Deployment modes

RPC, pool, and builder run together in one process or separately as networked services.

Test surfaces

Unit tests and integrated and modular ERC-4337 specification test targets are defined.

Tested chains

Ethereum, Optimism, Base, Zora, Frax, Arbitrum One, and Polygon PoS are explicitly listed as tested.