DynamoDB Transactions is the correct choice because it supports atomic all or nothing updates across multiple items and tables which keeps the TicketSwaps and WalletLedger tables consistent when a write must succeed as a unit.

DynamoDB Transactions provide ACID semantics through TransactWriteItems and TransactGetItems and they ensure that either all writes across the involved items and tables commit or none of them are applied. This transactional API is the intended mechanism for coordinating multi item updates in DynamoDB and it prevents partial writes that would leave the ticketing and wallet ledger data inconsistent.

DynamoDB Streams emit item level change events for asynchronous processing and auditing but they do not make writes atomic across items or tables so they cannot guarantee all or nothing updates.

DynamoDB TTL only controls time based expiry of items and it does not coordinate or group writes so it cannot provide transactional guarantees.

DynamoDB Indexes such as GSIs and LSIs improve query flexibility and performance but they do not enforce ACID transactions across tables and they are not used to perform atomic multi table writes.

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