All blockchain platforms currently have a critical problem that is preventing dapps from being both fully decentralized and performant: dapps cannot search blockchains in a decentralized manner.
Ethereum attempted to solve this problem with event topics. Dapps can ask a centralized RPC provider to scan events emitted by smart contracts. This revealed a number of critical issues:
- difficult to find endpoints
- unavailability - the endpoint may not be functioning
- there may be query limits unknownable to the dapp
- the provider may return incorrect results
- light clients do not work in practice
- subscriptions are unreliable
- queries can be very slow, for example when scanning the whole blockchain
- no standardized on-chain payment API
- tracking - providers can invade privacy
- lack of extensibility - no full text or AI search
- adds to gas cost
In fact some startups such as GhostLogs and Shadow are promoting the harmful idea that events should not be emitted on-chain at all, and centralized services should determine the events. This is a non-starter because in order to prove by light client that an event occurred it needs to be emitted by the contract on the blockchain.
Polkadot SDK has a much simpler approach to events than the EVM. Events are emitted on-chain, but there is no additional transaction weight to indicate that they should be indexed.
Both Ethereum and Substrate are implementing improvements to their light client protocols so they will actually be useable.
Acuity Index is a decentralized event index for all chain types. It has the following properties:
- a directory of endpoints stored on the Acuity blockchain
- redundancy - multiple endpoints can be queried ensuring no data is omitted
- well-defined query pricing
- both search and regular state queries supported
- results verifiable by light client
- both historic queries and subscriptions supported
- reduced gas cost - smart contracts can issue events without topics
- extensible - search can be extended off-chain, e.g. IPFS
The first chain type being targeted is Substrate. Acuity Index Substrate is a Rust library that can build an indexer for any Substrate chain. It was originally called Hybrid Indexer and was funded by two grants (1, 2) from the Web3 Foundation.
Acuity Index Polkadot is the first indexer built with Acuity Index Substrate. It can index Polkadot, Kusama, Westend and Rococo.
