> For the complete documentation index, see [llms.txt](https://docs.evoq.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.evoq.finance/advanced-mechanism/matching-engine/priority-queue-matching.md).

# Priority Queue Matching

While a queueing model could be used, it could be exploited by numerous accounts supplying tiny amounts, causing high gas costs for borrowers. Instead, we use a <mark style="color:blue;">**priority queue matching**</mark> system that sorts users by descending volume, ensuring that higher volumes are matched first. For each new request, the protocol arranges the top 8 opposite requests by volume to respond. Below is an example.

<figure><img src="/files/idXVbcsciWDT85PSpbTk" alt=""><figcaption><p>Example: Priority queue matching</p></figcaption></figure>

1. The initial state: Supply 1 is 800 USDC, supply 2 is 1000 USDC, and supply 3 is 500 USDC.
2. When borrow 4 is requested, the priority goes to supply 2.
3. After matching order 1, supply 1 remains at 800 USDC, supply 2 at 600 USDC, and supply 3 at 500 USDC.&#x20;
4. Thus, for borrow 5, the next priority is supply 1.
5. After matching order 2, supply 1 is 300 USDC, supply 2 is 600 USDC, and supply 3 is 500 USDC.
6. Hence, for borrow 6, the next priority is supply 2.
7. Then, matching order 3 is processed.
8. Unmatched amounts of supply 1 (300 USDC) and supply 3 (500 USDC) fall back to the underlying protocol.


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