Collection columns are a powerful feature of CQL that allow us to store multiple values in a single column. Most importantly, it's possible to discretely update single values in a collection without reading the collection's current contents or fully providing the new contents of the collection.

This capability is particularly useful when multiple processes might need to concurrently modify a collection. By avoiding the need to read and then fully overwrite a collection's contents, we avoid situations in which concurrent updates can lead to data loss and can support concurrent updates without resorting to optimistic locking.

Collections are best suited to datasets that are small and bounded. This is both because there is a hard upper limit on the amount of data a collection can hold, and because, when a collection is read, it is always read in full. For larger data sets, it is usually most appropriate to create a separate table whose partition key reflects the full primary key of the...