Transactional consistency / ACID guarantees.

Before you execute the query, you should be able to query any of the data, and after you execute the query, none of the data should be available. The mechanisms to make a transactional database is tricky.

Some databases, like CockroachDB, provides some built-in TTL capabilities.

But also- if you are having to delete huge ranges of data and do not care about consistency, you are probably looking at an analytical workload, and there would be better databases suited for that, like Clickhouse.