> For the complete documentation index, see [llms.txt](https://docs.mazze.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mazze.io/architecture/transaction-pool.md).

# Transaction pool

The transaction pool buffers incoming transactions, verifies them, and produces a packable set for block generation. It manages per-sender nonce order and keeps the account transactions of the native space and eSpace apart from the shielded lane.

## Main components

* `TransactionPool` - public API, ties to data manager and executed state.
* `TransactionPoolInner` - core data structures and packing logic.
* `DeferredPool` - per-sender nonce pools plus a packing pool.
* `PackingPool` - randomized packing algorithm with gas/price weighting.
* `AccountCache` - keeps nonce and balance hints for validation.

## Intake and validation flow

1. RPC/P2P submits a `SignedTransaction`.
2. `VerificationConfig` and `Machine` checks validate chain id, gas bounds, epoch bounds, and signature.
3. Transaction is inserted into the sender's `NoncePool`.
4. Ready contiguous nonces are mirrored into the `PackingPool`.

## Packing model

* Transactions are grouped per sender into `PackingBatch` objects to preserve nonce order.
* `PackingPool` is a treap-based structure that supports randomized sampling.
* Sampling considers block gas limits, block size limits, and minimum gas price.
* For EIP-1559 style pricing, the pool estimates the next base price using `compute_next_price` and adjusts the packing gas limit accordingly.

## Per-peer limits

Each peer may hold at most `max_trans_count_per_peer_normal` transactions in the pool (default 500,000). Transactions beyond the cap are rejected and counted.

## Space-aware packing

Mazze uses `SpaceMap`, with one slot per space:

* Native space is always packable.
* EVM space is packable only after the configured transition height.

The pool tracks gas usage per space and enforces per-space limits during block validation.

## Shielded lane

Shielded transactions have no sender, nonce or gas, so they live in their own lane, keyed by body hash, with an index of the nullifiers they spend.

* Admission checks the lane is active, the constant fee, the proof, the anchor, and that no nullifier is spent on chain or by another pooled transaction.
* The block generator packs them only at slot heights, in random order, up to `shielded_max_txs_per_block` per block.
* They are relayed with Dandelion++ (see [Networking](/architecture/networking.md)).

Details are in [The shielded lane](/shielded-space/shielded-lane.md#the-pool-lane).

## Key source files

* `crates/mazzecore/core/src/transaction_pool/mod.rs`
* `crates/mazzecore/core/src/transaction_pool/transaction_pool_inner.rs`
* `crates/mazzecore/core/src/transaction_pool/shielded.rs`
* `crates/mazzecore/packing-pool/src/pool.rs`
* `crates/mazzecore/packing-pool/src/packing_batch.rs`