When you're planning a DEX, there are a few decisions that shape everything else, and getting them wrong early can slow the entire project down.First is the blockchain choice. This affects transaction speed, fees, scalability, and the kind of users you’ll attract. Ethereum offers strong security and ecosystem support, but newer chains can give you lower fees and faster execution, which matters a lot for trading volume.Next comes smart contracts. This is basically the core engine of your exchange.