Indexers & Distributed Systems

The Indexer Pipeline and a Cursor That Survives Restart

Build the four-stage pipeline — ledger source, cursor, processor, store — and restart it mid-stream without losing or repeating work.

Commit the Cursor After the Effect, Never Before

Inject a crash between the two writes and measure both orderings: cursor-first silently loses an event, effect-first duplicates one — and only one of those is recoverable.

Idempotency Under At-Least-Once Delivery

Process a stream that duplicates and reorders events, twice over, and land on exactly the state a perfect exactly-once feed would have produced.

Surviving a Reorg: Roll Back to the Fork, Reapply the Branch

Detect that an incoming block forks below your head, unwind the orphaned blocks in reverse height order, and reapply the winning branch.

Transaction Status as a State Machine That Rejects

Encode Received/Validating/Submitted/Pending/Confirmed/Failed as a transition table whose default arm refuses illegal moves and leaves the state untouched.

Quorum Arithmetic: R + W > N, and What a Partition Does to It

Compute which (N, R, W) configurations guarantee a read sees the last write, then run a 3|2 partition and watch the minority side refuse both reads and writes.

Ordering Events Without a Clock: Lamport and Vector Stamps

Stamp a distributed event trace with both clock types and show the pair where Lamport reports an order that causality does not support.