ADR: use Postgres and Timescale for metrics

docs/adr/0002-use-timescale-for-metrics

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+# 2. Use Timescale with Postgres for Metrics
+
+Date: 2023-11-24
+
+## Status
+
+Accepted
+
+## Context
+
+We need to store certain metrics data, such as details about pull request and issues from GitHub and support requests from Slack. We're unable to get this information on demand using the APIs, because there's either no support with an existing Grafana plugin, it's not fast enough or it doesn't provide all the information we need.
+
+In same cases, we need to store a large amount of timeseries data. The Timescale extension to Postgres allows us to query that data in a very performant way and provides some nice functions so that we can perform operations, like bucketing the data, on the database server rather than when loading the dashboard.
+
+## Decision
+
+We will use Postgres with the Timescale extension to store our metrics data.
+
+## Consequences
+
+We'll be able to store all the different types of data that are needed for our dashboards.
+
+The Postgres database will be hosted using a managed Digital Ocean service and backed up using Snapshooter. We believe this will keep the operational burden to a minimum.