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# Mempool

### Transaction Mempool Configuration in BitNet

The **mempool** is where incoming transactions wait before being included in a new block. BitNet supports two mempool modes for handling transaction flow and prioritization.

#### FIFO Mempool (Default)

By default, BitNet uses a **First-In, First-Out (FIFO)** mempool strategy. Transactions are processed in the exact order they arrive. This order applies both to:

* **Gossiping** transactions to peers
* **Including** them in the next block

This method ensures fairness but doesn't prioritize high-fee transactions.

***

#### Prioritized Mempool (v1)

BitNet also supports the **prioritized mempool** introduced in Tendermint v0.35. In this mode, transactions are **ranked by fee or custom priority logic**.

**Key Features:**

* Transactions with **higher fees** are selected first for inclusion in the next block.
* If the mempool is full, **low-priority transactions are evicted** in favor of higher-paying ones.
* This is ideal for **EIP-1559-style fee markets**, where users can set a base fee and a tip.

{% hint style="danger" %}
Transaction gossiping still follows FIFO even in prioritized mode — only **block inclusion** is affected by priority.
{% endhint %}

***

#### Enabling Prioritized Mempool

To activate the prioritized mempool in your node, update the `config.toml` file:

```toml
[mempool]
version = "v1"  # Use "v0" for FIFO, "v1" for prioritized
```

Then restart your node:

```bash
bitnetd start
```

***

#### Use Cases for Prioritized Mode

* **Validators** can maximize revenue by automatically selecting high-fee transactions.
* **Users** can ensure faster inclusion of time-sensitive transactions by adding priority tips.
* **Applications** can implement dynamic fee estimation based on mempool state.


---

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