Do indexers sign their indexed data for verification?

Yes, proofs of indexing (POIs) are utilized for this purpose. POIs are mathematical proofs that are derived from the data stored in the database. These proofs are employed within the network to ensure that an Indexer is accurately indexing the subgraphs they have been assigned.

To be eligible for indexing rewards, an Indexer must submit a POI for the first block of the current epoch when closing an allocation. This POI serves as a digest for all entity store transactions related to a specific subgraph deployment, up to and including that block.

In addition to submitting POIs, Indexers also sign attestations for every query response. This means that they can be slashed not only for inaccurate query responses but also for invalid POIs. This serves as a mechanism to maintain the integrity and reliability of the indexing process and ensures that Indexers are accountable for the accuracy of their indexing and query responses. If an Indexer submits inaccurate or faulty data, they are at risk of facing slashing penalties to uphold the network's standards.