A company runs a custom accounting application on Amazon EC2 and wants to migrate the data to a managed AWS service that requires minimal operational support and provides immutable, cryptographically verifiable logs of data changes. Which solution is the most cost-effective?

Amazon QLDB is the most cost-effective solution because it is specifically designed for immutable, cryptographically verifiable transaction logs, perfectly matching the requirement for immutable and verifiable data changes. It is a fully managed ledger database, minimizing operational overhead. Amazon Redshift is a data warehouse service optimized for analytical queries, not for immutable transaction logs and is generally more expensive for this use case. Amazon Neptune is a graph database, suitable for highly connected datasets, but not for the specified ledger requirements. Amazon Timestream is a time-series database, ideal for time-stamped data, but it doesn't inherently provide the cryptographic verifiability of a ledger.