# Match Limits

Matching is executed price-level by price-level in **O(1) gas**. Takers consume up to their remaining size at each level and stop once they are filled or when their slippage guard trips.

## Why There Is No Match Limit

* **Level batching** – `_matchAtPriceLevel` flushes all maker volume stored in `PriceLevelData` in one step, regardless of how many individual orders are resting at that price.
* **Deterministic gas** – each additional price level adds a predictable cost. There is no per-maker loop, so a surge of tiny orders at the same price cannot grief takers.
* **Simplified UX** – the execution levers are `ExecutionType` (`Standard`, `IOC`, `FOK`) and the price/amount bounds the taker sets.

## Interface Compatibility

* `createBuyOrder` / `createSellOrder` do not take any match-limit parameter, and `IOrderBook.OrderParams` omits that field.
* There is no `MatchLimitReached` event. Downstream systems should monitor `OrderReduced`, `OrderCancelled`, and taker execution events instead.

SDKs should not pass any match-limit argument; the call will revert if extra parameters are supplied.

## Current Gas-Safety Recommendations

1. **Choose the right execution type** – use `ExecutionType.IOC` when takers must avoid resting remainders, or `ExecutionType.FOK` when partial fills are unacceptable.
2. **Sanity-check limit prices** – even though per-level costs are flat, walking thousands of price levels can still burn gas. Keep reasonable price caps/floors in place.
3. **Simulate before submitting** – `previewTakerOrder` provides the exact levels touched and quote usage for a hypothetical trade. Front-ends should call it to surface worst-case depth.
4. **Cap off-chain loops** – indexers or bots that scan the book should continue to guard against pathological depth.

The result is a simpler runtime that honours familiar execution semantics without extra match-limit toggles.


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