Pool Reserves

How It Works

A standard AMM liquidity pool holds two token reserves — for example, 500 ETH and 1,000,000 USDC. The ratio between these reserves defines the current trading price: 1,000,000 / 500 = 2,000 USDC per ETH. Every swap changes the reserves — buying ETH removes it from the pool (reducing ETH reserves) and adds USDC (increasing USDC reserves), shifting the price.

The constant product formula (x * y = k) constrains how reserves can change. After every swap, the product of the two reserves must remain equal to the invariant k (minus fees). Larger reserves mean a larger k, which translates to deeper liquidity and lower price impact per trade.

Pool reserves are publicly readable from the smart contract and are displayed on analytics platforms. Tools like DexScreener show both the token quantities and their USD value (the pool's TVL). Large imbalances in reserves — where one token dominates — can indicate significant price movement or potential liquidity issues.

Why It Matters in DeFi

Pool reserves are the fundamental measure of liquidity quality. A pool with $10 million in reserves can handle much larger trades with minimal slippage compared to a pool with $100,000. Before executing any swap, experienced traders check the pool reserves to estimate their price impact and determine whether the pool can handle their trade size.

Changes in pool reserves over time tell a story about market activity. Decreasing reserves of the base token (like ETH or USDC) alongside increasing project token reserves indicate net selling pressure. The reverse pattern indicates net buying. Monitoring reserve changes complements price chart analysis for understanding token dynamics.

Real-World Example

A TOKEN/ETH pool has reserves of 10,000,000 TOKEN and 100 ETH, implying a price of 0.00001 ETH per TOKEN. A trader wants to buy TOKEN worth 10 ETH. Using the constant product formula, this trade would receive approximately 909,091 TOKEN and shift the reserves to 9,090,909 TOKEN and 110 ETH. The new implied price is 0.0000121 ETH per TOKEN — a 21% price impact. The same trade in a pool with 10x larger reserves would have only about 2% price impact.