Arbitrum uses a technique known as transaction rollups to record batches of submitted transactions on the Ethereum main chain and execute them on a cheap, scalable layer 2 sidechain while leveraging Ethereum to ensure correct results.
This process helps to offload most of the computational and storage burden Ethereum currently suffers from while enabling new classes of powerful layer 2 scaling solutions.
Optimism is an Ethereum Layer 2 scaling solution that uses optimistic rollups to achieve far lower fees, far lower latency, and far greater throughput versus Ethereum Layer 1 alone while also providing a world-class developer and user experience.
In July 2021, Uniswap V3 launched on Optimism, projecting the following benefits for users:
Speed with security
Gas costs on optimism are 35 times cheaper than on Ethereum
Optimistic rollups publish state changes to the main chain with minimal inspection and fraud checking allowing for additional speed
Uniswap estimates that, based on usage stats on the main chain, Optimistic Ethereum will offer up to 10x cost savings
Uniswap V3 launched in early May 2021 and quickly became the exchange with the most trading volume.