📖 User Manual | 🤝 Contributing | 💾 Changelog | Twitter (@KtorZ)

Kupo is fast, lightweight and configurable chain-index for the Cardano blockchain. It synchronizes data from the blockchain according to patterns matching addresses present in transaction outputs and builds a lookup table from matches to their associated output references, values, datums and scripts.

The project keeps a changelog 💾 in which all recent-but-not-yet-released changes can be seen. Changes in the changelog have been implemented and are available in latest builds from the master branch.

The projects boards 🎯 list planned tasks that haven't been implemented but have reached enough maturity to be well-defined and scoped.

Finally, discussions 💡 contains ongoing discussions regarding the future of Kupo, with design decisions still under consideration.

Status	Description
	Docker image pulls
	Nix build, providing static binary executables as artifacts.
	User manual and API reference deployment.
	Test code coverage. Learn more about the testing strategy.

Kupo is well-suited for small (or large) applications which need either:

• a global chain index for resolving outputs by address, policy id or output reference;
• a on-the-fly monitoring of an address, policy id or specific transaction output over a short period of time.

It runs in constant memory and is blazing fast. Yet, its use-cases are limited. Here below we provide some possible alternatives with different trade-offs:

Solution	Ecosystem	Key difference(s)
	Rust	Oura in itself does not provide any chain-indexing, but it supports pluggable sinks where filtered data from the Cardano blockchain can be dumped into (e.g. Elastic Search or Kafka). It also supports a wider variety of events. All-in-all, a good fit for more elaborate solutions.
	Go	Similar to Oura, Adder is is an event-emitter coupled with filters. Therefore, it requires a backend storage or an additional solution for handling and serving events coming from the chain. Like Kupo, it supports a variety of filters on addresses or assets albeit in a more direct way.
	Java	Yaci Store is a small component built on top of the Yaci libraries -- a collection of Java libraries for interacting with the Cardano networking protocols. It can be used as a library to deal with an event stream similar to Oura and Adder, or as a full blackbox solution storing into various storage solutions (SQLite, Redis, MongoDB, ...).
	Rust	Scrolls provides (at this stage) an in-memory aggregation engine via Redis. It allows applications to watch and react instantly on the evolution of some aggregated metric (see Scrolls' README for details about what metrics are supported). Because the data is fully stored in-memory, it is not possible to index the entire chain without resorting to large memory requirements. Hence it is more tailored to specific handpicked pieces of information. It also synchronizes blocks from the chain using the node-to-node protocol which means that it can do so on any remote node relay, but it is also slower (because a more defensive protocol) than the node-to-client protocol upon which Kupo relies.
	Rust	Carp is a modular blockchain indexer built on top of Oura; it synchronizes data in a PostgreSQL database based on behaviors described in tasks (Rust standalone plugins). Some pre-defined common tasks are already available, other can be written on-demand to fit one's use case. As a primary interface, Carps fully relies on PostgreSQL.
cardano-db-sync	Haskell	cardano-db-sync synchronizes ALL data from the Cardano blockchain, whereas Kupo focuses only on transaction outputs. This comes with obvious trade-offs in both on-disk storage, runtime requirements and performances. Kupo is usually an order of magnitude faster for retrieving outputs by address, stake address or policy id. Note also that like Carp, cardano-db-sync's primary interface is a PostgreSQL database whereas Kupo offers a higher-level HTTP API over JSON.

A big thank to all our sponsors 💖.