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...).

How to tunnel 2 AWS networks and don't use AWS services. Most of manual show how to do it, but without high availability. Here we can have asymmetric routing or any other.