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# Algorand Specifications

The Ledger [module](https://github.com/algorand/go-algorand/tree/18990e06116efa0ad29008d5879c8e4dcfa51653/ledger) includes a collection of auxiliary components known as _Trackers_.

Trackers are state machines that evolve by consuming blocks from the blockchain.

Although logically stateless, meaning Trackers can rebuild their state from scratch by replaying all blocks since the _genesis block_ every time, the reference implementation designs them to persist their state to speed up Ledger reconstruction.

Trackers are widely used in `go-algorand` to maintain efficient, read-optimized views over different aspects of Ledger state.

Below is an overview of the main Trackers and their responsibilities:

- **Account Tracker**  
  Maintains account states up to a given round. Key methods include:  
  - `Lookup(round, address)`: Retrieves the state of the account (`address`) at the specified `round`.
  - `AllBalances(round)`: Returns all account states at the specified `round`.
  - `Totals(round)`: Returns aggregate account totals for a given `round`, which is useful when querying for total account balance in the cryptographic sortition.

- **Recent Transactions Tracker**  
  Uses the [Transaction Tail](https://specs.algorand.co/ledger/non-normative/ledger-nn-transaction-tail) to efficiently check whether a given transaction ID (`txid`) was included in a recent block.

- **State Proof Verification Tracker**  
  Maintains the necessary context to verify State Proofs (see State Proof [normative specification](https://specs.algorand.co/crypto/crypto-state-proofs#state-proof-validity).

- **Voters Tracker**  
  Tracks the [vector commitment](https://specs.algorand.co/crypto/crypto-vector-commitment) representing the most recent set of online accounts participating in the [State Proofs](https://specs.algorand.co/crypto/crypto-state-proofs).

- **Catchpoint Tracker**  
  Monitors the Catch-Up process used during node synchronization (see the [non-normative specification](https://specs.algorand.co/node/non-normative/node-nn-sync)).