> ## Documentation Index
> Fetch the complete documentation index at: https://cosmos-docs-selective-ibc-merge.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Learn about rate limit middleware, a middleware that can be used in combination with token transfers (ICS-20) to control the amount of in and outflows of assets in a certain time period.

Learn about rate limit middleware, a middleware that can be used in combination with token transfers (ICS-20) to control the amount of in and outflows of assets in a certain time period.

## What is Rate Limit Middleware?

The rate limit middleware enforces rate limits on IBC token transfers coming into and out of a chain. It supports:

* **Risk Mitigation:** In case of a bug exploit, attack or economic failure of a connected chain, it limits the impact to the in/outflow specified for a given time period.
* **Token Filtering:** Through the use of a blacklist, the middleware can completely block tokens entering or leaving a domain, relevant for complicance or giving asset issuers greater control over the domains token can be sent to.
* **Uninterupted Packet Flow:** When desired, rate limits can be bypassed by using the whitelist, to avoid any restriction on asset in or outflows.

## How it works

The rate limiting middleware determines whether tokens can flow into or out of a chain. The middleware does this by:

1. Check transfer limits for an asset (Quota): When tokens are recieved or sent, the middleware determines whether the amount of tokens flowing in or out have exceeded the limit.

2. Track in or outflow: When tokens enter or leave the chain, the amount transferred is tracked in state

3. Block or allow token flow: Dependent on the limit, the middleware will either allow the tokens to pass through or block the tokens.

4. Handle failures: If the packet timesout or fails to be delivered, the middleware ensures limits are correctly recorded.