The document discusses building a custom data source for Grafana using Vert.x to retrieve time series data stored in MongoDB. It describes how to connect Grafana and MongoDB through a three-tier architecture using a Vert.x microservice. The microservice would handle splitting requests, querying the database in parallel, aggregating results, and performing additional processing before returning data to Grafana. Vert.x is well-suited for this due to its asynchronous, reactive, and scalable nature. Sample code is available on GitHub to demonstrate the approach.