Overview
Dolos is a lightweight server program that keeps an up-to-date copy of a blockchain's records and answers questions about them for apps, wallets, and explorers. Development teams run it when they need their own source of chain data, such as balances and transaction history, without running a full node, the heavier software that stores and checks everything on the network1.
Dolos is built for Cardano by TxPipe, a software team that makes tools for Cardano developers in the Rust programming language. Cardano nodes usually act as block producers, which create new blocks, or relays, which pass data between nodes; Dolos adds a third role, the data node2. It talks to the network through Pallas, TxPipe's Rust toolkit for Cardano, and the code is open-source under the Apache 2.0 license2.
Key Features
- Works with tools teams already use. Dolos answers requests in the same format as Blockfrost, a hosted data service, and covers the requests most transaction-building tools need3. Dolos also answers coin lookups in the format of Kupo, a chain index that finds coins by address, and provides the node connection that cardano-cli and Ogmios, two common developer tools, expect1.
- A live data stream for apps. A connection called UTxO RPC, built on the gRPC messaging standard, lets apps query chain data, get notified when something changes, and submit transactions, including from a web browser4.
- Keep only the history you need. Operators pick between storing only the current chain state, a rolling window of recent history such as days or weeks, or the full chain archive, trading disk space for how far back queries reach1.
- Start from a snapshot. Instead of downloading the chain block by block from a peer, Dolos can start from a Mithril snapshot, a certified copy of chain data, or from an export of another Dolos node5.
- Transactions checked before they go out. A built-in waiting area for pending transactions runs Cardano's validation rules locally before submission and lets an app build new transactions on top of ones that are still in flight1.
What to Expect
Dolos is aimed at developers and infrastructure teams behind DApps, wallets, and block explorers1. Getting started takes a few commands. You install it through Homebrew, a Linux shell script, Windows PowerShell, or Docker, then an interactive setup command asks a handful of questions, configures the node, and pulls in chain history6. One command then syncs with the network and serves data. Larger setups can split syncing and serving into separate processes7.
For block data, Dolos depends on an upstream Cardano node it trusts instead of checking consensus, the network's agreement process, on its own, and it does not create blocks1. It is a companion to the network's full nodes, which it relies on for fresh blocks.
