blockchain – How to calculate how a certain transaction impacts a token price?

How to Calculate Token Price Impact of Large Trades in Decentralized Finance (DeFi) Environments

I am developing a tool to analyze the impact of large trades on token prices within a Decentralized Exchange (DEX) environment, specifically on the Polygon network using the Quickswap Router contract as a case study. My goal is to programmatically estimate the price movement caused by significant transactions.

Scenario:

Assume we’re observing the Polygon mempool for transactions directed towards the Quickswap Router contract. We detect a transaction swapping a substantial amount of a stablecoin (denoted as S) for a token (denoted as R). The transaction details are as follows: $34,000 of S is exchanged for R tokens priced at $7.21 each. Ignoring transaction fees, this equates to purchasing approximately 4,715.67 R tokens.

Objective:

I want to calculate the post-transaction price of R in the scenario where the liquidity pool’s initial state is as follows:

• Liquidity Pool Size (Initial): 100,000 R and 721,000 S (indicating a 1R = 7.21S or $7.21 price per R token).
• Order Size: $34,000 worth of S to buy R.
• Current R Price: $7.21 per R.

Approach:

I used the Constant Product Market Maker (CPMM) model for simplicity, excluding factors like slippage tolerance and trading volume from the calculation. The process is:

1. Calculate the Number of R Tokens Bought: Divide the order size by the current R price.
2. Update the Liquidity Pool: Subtract the R tokens bought from the pool and add the S spent.
3. Calculate the New Price of R: Determine the new price based on the updated liquidity pool ratio.

Calculation:

After executing the trade, the liquidity pool is adjusted, and the new price of R is calculated. However, I’m looking for feedback on this approach and any suggestions for more accurate or efficient methods to estimate the price impact of large trades in DeFi settings.

Does anyone have insights or improvements to offer on this calculation method? Any advice or alternative strategies would be greatly appreciated.