earlier today @heliuslabs launched a new RPC method, getTransactionsForAddress (gTFA) let's talk about how it works under the hood solana transactions typically reference 6-10 accounts (up to ~256) when you query "get me the history of account X", you are asking the RPC to scan transactions and find the ones that include X in their list of accounts this is essentially trying to find a needle in a haystack you can't simply add a standard index on the "accounts" array at scale – databases struggle with indexing variable length arrays the solution: we built our own index, with one entry per unique (transaction, account) pair this is no small feat – there are ~493 billion transactions (and growing) our index currently holds over 2.3 trillion (!) rows despite the size, the P50 lookup time is ~8ms under production load and we have many other indices to power lookups by slot, time, status, etc all running on purpose-built bare metal hosts with petabytes of top-of-the line NVMEs, replicated across multiple regions tldr – we suffered so you don't have to enjoy