docs(prometheus): high availability with extra steps

knowledge base/cortex.md

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+# Cortex
+
+> TODO
+
+Intro
+
+<!-- Remove this line to uncomment if used
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+   1. [Sources](#sources)
+
+## TL;DR
+
+<!-- Uncomment if used
+<details>
+  <summary>Setup</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Usage</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+- [Website]
+- [Codebase]
+- [Prometheus]
+
+Alternatives:
+
+- Grafana's [Mimir]
+- [Thanos]
+
+### Sources
+
+- [Documentation]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+[mimir]: mimir.md
+[prometheus]: prometheus.md
+[thanos]: thanos.md
+
+<!-- Files -->
+<!-- Upstream -->
+[codebase]: https://github.com/cortexproject/cortex
+[documentation]: https://cortexmetrics.io/docs/
+[website]: https://cortexmetrics.io/
+
+<!-- Others -->