The difference is persistence provided by a "store", not the semantics of the data space (which is a mapping from keys to values). Further, a hash is one of th

The difference is persistence provided by a "store", not the semantics of the data space (which is a mapping from keys to values). Further, a hash is one of the alternative implementation strategies for a key-value space; your typical in-memory "database" will likely opt for hashes, while issues regarding disk access latencies favor tree structures.