Motivation

Apache Ignite provides a consistency guarantee, each backup should contain the same value for the same key, at least eventually.
But this guarantee can be violated because of ... bugs.

And yes, we had some and fixed them.
But, is there any chances we fixed all and will not write new? :)

So, we have to have additional failover layer to check and fix such violations.

...

1) LWW and any other strategy do not guarantee that the correct value will be chosen.
We have to record the event contains all values and the chosen one.
The event will allow to
- got we have an inconsistent state situation
- investigate which value is correct manually and refix if necessary

1.1) Seems, it's not possible to fix any cases.
For any transactional cache we able to perform pessimistic serializable transaction per key.
But, atomic caches cannot be fixed this way.
Some Entry Processor can be used or we can finally implement thread per partition for atomic caches.

2) Consistency guard able to produce the following problems
- replace hot data with cold data
We have to have special configuration property allows or restricts to check (read) data available only at the persistence layer
- decrease throughput/latency metrics
Some throttle feature should be implemented

...