# Indexes Indexes are needed to map Solana’s block numbers, transaction signatures, and addresses to their respective Content Identifiers. These indexes have been developed as part of this project. There are four content identifier indexes that the Old Faithful index generation can provide: * **slot-to-cid**: Lookup a CID based on a slot number * **tx-to-cid:** Lookup a CID based on a transaction signature * **cid-to-offset-and-size**: Index for a specific CAR file, used by the local RPC server (see above) to find CIDs in a car file * **sig-exists**: Index to check whether a specific signature exists in an epoch. In addition, Old Faithful supports an index `gsfa` that maps Solana addresses to a list of transaction signatures. This allows Old Faithful to support “Get Signatures For Address.” --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.old-faithful.net/introduction/architecture/indexes.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.