An order book is a system to list all open buy and sell orders. Almost all exchanges use it due to its transparency and efficiency. An order book is the better choice for decentralized derivatives exchanges since it can bootstrap most market trading volume and requires less capital to achieve the same level of liquidity as AMM's.
Quantitive strategies run by crypto funds account for most of the trading volume in crypto derivatives markets.AMM is incompatible with this strategy due to its flaws, such as impermanent loss, slippage, and low transaction speed. As a result, trading or even backtesting on AMM is infeasible. Also, market makers and professional investors used to centralized exchanges will find it easier to transfer to a decentralized order book exchange. More market makers mean better liquidity and smaller spreads, which bring a better trading experience. Lastly, some of the most traded crypto assets are traded via the order book system.
Thus, an order book system can create a positive feedback loop: more trading volume can provide better trading experiences, and better trading experiences can attract more trading volumes.
Aboard is currently deployed on Arbitrum Mainnet. Arbitrum is an Ethereum Layer-2 solution that utilizes optimistic rollup technology. For more details, Harry, Steven, and Ed (2018) discuss the mechanism of the Arbitrum network in their white paper. Aboard chooses Arbitrum One based on three main reasons：
Arbitrum is fully EVM compatible, so code for Ethereum will also work on Arbitrum. This allows popular Ethereum projects to adapt to L2 solutions quickly. According to Defi Llama, Arbitrum currently has the most TVL at $917.19 million, only 3 billion short of the Ethereum layer-1. A prosperous ecosystem can bring considerable liquidity, one of the core factors for the trading experience.
Ethereum is currently the most popular public Mainnet for blockchain projects. More than 3,000 decentralized applications are running on the Ethereum blockchain. Such popularity leads to a considerable increase in the Ethereum gas fee and its volatility. The average daily gas price went from 58 Gwei in August 2015 to 158 Gwei in January 2022. Consequently, High transaction costs make trading on layer-1 almost infeasible to serious traders.
As a layer 2 solution, optimistic rollups can significantly reduce the trading cost. Arbitrum reduces the trading cost by more than 50x for most works loads and even more with the upcoming Nitro upgrades.
Compared with other rollups, Optimistic rollups are more decentralized since they provide more transparency and do not require dedicated hardware or massive parallelism for scalability. On Arbiturm One, anyone can check the content of the chain. Therefore, the chain is less decentralized as only the participants with the tools can forward the progress.