Transaction Deduplication
Core Protocol · Abyss
Solana's mechanism for preventing the same transaction from being processed twice within a slot or across consecutive slots. Each transaction is uniquely identified by its first signature; the runtime maintains a status cache of recently processed signatures spanning roughly 150 slots (~60-90 seconds). If a transaction with an already-seen signature arrives, it is silently dropped. This cache is why retry logic can safely resubmit the same signed transaction without risk of double-execution, and why transactions with expired blockhashes are rejected even if the signature is novel.