For a matching transaction or event, Moralis Streams normally sends an confirmed: false webhook when it first appears in a block or Solana slot, followed by a confirmed: true webhook after the chain's confirmation threshold. A chain reorganization can change unconfirmed data, so wait for the confirmed delivery before treating it as final in a workflow that requires finality.
Confirmation thresholds vary by chain and can change. Use the current Streams supported chains and confirmation threshold table instead of a fixed list in this article. See Streams pricing for how confirmed and unconfirmed deliveries affect usage.