• @Bheem Elastic APM by virtue of being from Elastic is tightly coupled to using ElasticSearch as the datastore. We are datastore agnostic and provide modular architecture to support new datastores. Currently we support Clickhouse but other relevant dbs can be supported on community demand.
• Elastic is not the best DB for unified observability because it was made to search structureless logs whereas metrics (being time series data) and traces are quite structured.
• Elastic is primarily used for logs. Hence, Elastic APM is very log focused. They obtain metrics from logs. If you try to run Elastic APM, under the hood you run Elastic search and Kibana which were made for logs. We use OLAP databases which can crunch aggregates from raw data very fast. When the world is moving towards structured logging, I see more users moving to columnar/OLAP databases.
In short, faster query + cheaper storage costs.