Platypus is a decentralized exchange native to Avalanche focused on trades of highly correlated assets like stablecoins. It innovates upon the traditional stableswap concept with single-sided liquidity provision.
Platypus innovated upon the stableswap concept through the introduction of single-sided liquidity. The key concept underpinning Platypus' design is asset liability management (ALM). With a traditional AMM, users who provide liquidity receive LP tokens in return that represent partial ownership of a pool. Liquidity pools consist of two or more assets and trades against that pool by design adjust the balance over time. So when LPs withdraw their assets, they often receive a different amount than they originally deposited due to impermanent loss. With ALM, Platypus records the liability upon a user deposit and are given LP tokens that exact amount and exact token deposited. This allows each token to grow oragnically through supply and demand.
Platypus charges a series of fees on its platform including swap fees (haircut) and deposit/withdrawal arbitrage fees. The haircut fee varies by pool and is used to support and incentivize the platform's operations. A portion of haircut remains in the AMM based on a retention ratio. The retention ratio is initially set at 100% so all fees collected remain with Platypus. Platypus implements a withdrawal fee to deter arbitragers from draining funds from the pool that can harm the protocol's long-term financial health. Similarly, the protocol also charges a deposit fee to counter such attacks.
You earn swap fees for providing liquidity on Platypus. Currently, all rewards are paid in inflationary PTP token emissions. When the retention ratio decreases below 100%, LPs will earn the difference in swap fees. You can also stake PTP (vePTP) to boost their liquidity mining rewards (paid in PTP).