IT

Redis - nice tools for store key-value data in different formats. Here pretty easy way to create failover for replication. Sometime named as redis cluster, but is it not true, just few (prefer 3 for sentinel quorum) servers with one master and slaves in different configuration (slave from slave, slave by priority. local slave...).

What we have: Telegraf with send stats to two influxdb servers and dashboard with we need point to only one server. Also we have Nagios as InfluxDB health monitoring.

Sometimes you need roll out part of application (after code refactoring, as example) to prod. Here pretty easy way how to do it with Haproxy

After some migration between applications versions you need to keep backward compatibility. Here example of easy way how to redirect lot of links to new location for Haproxy.  (example for Nginx )