Liquidity pool: the engine behind DEX trading

How Pools Replace Order Books

A liquidity pool is a smart contract holding reserves of two or more tokens. Traders can swap one token for the other directly with the pool, and the pool's pricing follows a formula rather than matching individual buyers and sellers. The original and most common formula is the constant product rule, $x \cdot y = k$, where $x$ and $y$ are the token reserves and $k$ stays constant.

Anyone can become a liquidity provider by depositing equal value of both tokens into the pool. In return, they receive LP tokens representing their share and earn a cut of the trading fees—usually 0.3% per swap on Uniswap-style pools, sometimes lower for stable-asset pools. The more you provide and the more the pool is traded, the more you earn.

The math has tradeoffs. Large trades shift the reserve balance and therefore the price, producing significant slippage. Liquidity providers also face impermanent loss—the gap between holding the assets passively and providing them to a pool when prices diverge. Modern designs like concentrated liquidity, stable-asset curves, and hybrid models try to push throughput up while reducing both effects.