Hi @baris ,
Just to provide some updates:
I tested the w=<number of mongod instance> in my local and it works. However, in our real environment, we're using Amazon DocumentDB, which unfortunately doesn't support user defined write concern and ignored the configuration, it will always use the default MAJORITY.
Based on the suggestion by DocumentDB, I guess we should use readPreference=primary in this case to ensure read-after-write result. Assuming DocumentDB will manage it so that for reads after write will prioritize primary and at the time routes other reads to secondary to avoid overloading primary. Just curious why we need to configure this instead of being a default behavior.