What happens when we directly send tokens to Uniswap pair?

Question

This is about Uni V2 pools.

So usually we call the function addLiquidity to add liquidity, but the function decides how many tokens should be added depending on the reserves.

What if we directly send the tokens? How does that not affect the price of token.

Suppose the liquidity is 1000: 1000 for two tokens, token1, and token2 and suddenly I sent 10k token2 using a normal ERC20 transfer, how does this not affect the price?

Answer 1

Uniswap V2 is using the reserve amounts for calculation, not token balances. When you send the tokens directly to the pool's address, uniswap actually does not know you are doing this, because you are interacting with the token contracts, not uniswap's contracts, i.e. updating your balance and the balance of the pool's address in the token contract.

Answer 2

Transferring tokens directly won't effect the price until you call either the sync or mint functions. That will update the reserves which will update the price.

That's ultimately how the token swaps effect the price anyway.