What Is the Primary Benefit of Using the Constant Sum Formula (X+y=k) near the Stablecoin Peg?

The primary benefit of the constant sum formula (x+y=k) is that it provides virtually zero slippage and infinite liquidity near the 1:1 price peg. This is because the price remains constant regardless of the trade size, as long as the reserves are not depleted.

This behavior is ideal for stablecoins, which are intended to trade at a constant value. The stableswap invariant uses this constant sum behavior near the peg to maximize capital efficiency.