Aptos Hides Trades Until Their Order Is Locked

Key Takeaways

Why a visible pending trade can cost its sender

In its October 12 announcement, Aptos said encrypted mempool was live on mainnet. A mempool holds pending transactions before they are included in a block. When their contents are visible, observers can inspect instructions before execution.

Consider a hypothetical swap large enough to move a token’s price. A bot that sees the pending order could try to buy first, let the user’s swap push the price higher, then sell afterward. This sequence, known as a sandwich attack, can leave the user with worse execution. It depends on seeing the instruction while there is still an opportunity to trade around it.

Encryption removes that view of the transaction’s payload—the function being called and its arguments—during ordering. It does not promise...