# Storage and snapshots

State persistence is provided by the `mazze-storage` crate. It combines a Merkle Patricia Trie (MPT) with snapshotting and delta layers to balance performance and history retention.

## Storage layers

* Delta MPTs: append-only changes between snapshots.
* Snapshot MPTs: compact state snapshots at selected epochs.
* State DB backend: MDBX by default, configurable via `MdbxConfig`.

## StorageManager and state access

`StorageManager` and `StateManager` provide:

* Read/write access to the current state.
* Snapshot creation and pruning.
* Proof generation and state sync support.

## Snapshot policy

`StorageConfiguration` controls:

* `snapshot_epoch_count` and `era_epoch_count`.
* Extra snapshots for sync (`ProvideExtraSnapshotSyncConfig`).
* Cache sizes and open snapshot limits.
* Directory layout under `storage_db/`.

## Interaction with consensus

`BlockDataManager` keeps a `StateAvailabilityBoundary` describing which epoch states can be read. This allows full nodes to prune old state while still serving recent queries.

## Key source files

* `crates/dbs/storage/src/lib.rs`
* `crates/dbs/storage/src/state_manager.rs`
* `crates/dbs/storage/src/impls/storage_manager/snapshot_manager.rs`
* `crates/dbs/storage/src/impls/merkle_patricia_trie/mod.rs`
* `crates/mazzecore/core/src/block_data_manager/mod.rs`