Secondary indexes that never lag
DynamoDB's global secondary indexes are eventually consistent: a write to a base table
propagates to its GSIs asynchronously, so a query against a GSI can briefly miss an item
that a GetItem on the base table already returns. fdyno maintains every index inside
the same transaction as the base write, so this window does not exist. That choice buys a
simpler mental model and costs throughput; both halves are worth spelling out.