There is a fair few questions here, let me break them down:
When we use Couchbase server as a caching provider for a caching solution what specific configurations should be done/focused when setting up a bucket in couchbase server for caching?
This really depends on the use case and what the performance of the underlying data store. I would say the big question here is what bucket type to use: Couchbase Bucket or ephemeral. Our documentation covers the differences between the two. For a cache usecases Couchbase Bucket protect against cold cache situations. Where Ephemeral buckets have a reduce TCO as everything is stored in memory, saving the need for disks. Depending on the ejection policy used it will automatically removed old items when the bucket is full, making it easier to use as a cache.
Lets say I already use couchbase server as the data store for a springboot or nodejs based micro service.Can I use plugins like couchbase-spring-cache and further improve the performance of already couchbase backed service?
When the data store is Couchbase Server in most cases it makes no sense to put another Couchbase Cluster in front of it as a cache. It just makes the overall system more complex. Couchbase Server combine the Database and Cache all in one solution so in this case it makes sense just to increase the size of the existing cluster.
Or you are recommending couchbase as a cache layer for services which are lacking performance and backed my RDBMS like postgres my sql?
This is a very common use case for Couchbase Server, which in a number of case leads to Couchbase Server replacing the RDBMS in the long term. Why have two system, when you can have one that does both?
According to this document you can use couchbase with default configuration in caching implementations leveraging memory first behaviour.IF default configuration is the way to implement caching using memory reads and writes how couchbase recover from a failure.In mongodb there is journalfile to refer to recover from failure.Does couchbase get similar approach to recover from failure when memory first write nodes failed?
Couchbase Server provides complete flexibility when it comes to ensuring the data is safe. By default Couchbase Server will response when the 1st nodes has the data in memory. It will then asynchronously send the data to the replicas and write it to disk. For use cases that needs more protection, the application can ask for the write to only be successful once the data has been committed to disk or replicated to one or more nodes in memory or even committed to disk on multiple nodes. For more details please see durability.