Comment by gane5h

We store our event stream data in Elasticsearch. Two features that made it appealing:

  * the ingest-side can be scaled up by adding more shards
  * the query-side can be scaled up by adding more replicas

To compute rollup analytics, we make heavy use of Elasticsearch's aggregation framework to compute daily/weekly/monthly/quarterly active users.

From my understanding Postgres has many of these features, but the distributed features of ES are killer!