Additionally, the ability to pin a database at a specific point in time is useful for APIs. For one, on pagination so that you don't see pages change out underneath as records are updated. Another is in APIs that join configuration values with time-series data or aggregations. If our data decisions drive revenue, for example, looking at 2018-08-31 revenues with today's business data has a lot less insightful value than being able to see them with other data pinned at that same date. Pointing the queried DB to a fixed timestamp in Datomic is free.
One of the motivations for Crux was that `as-of` queries still weren't powerful enough for what the business really needed, which was something like `as-of` that could cope with retroactive corrections for out-of-order and delayed ingestion (of upstream transaction data).
