I would like to get some insight information about how an alias switch works.
We observed a scenario in our cluster (only 3 nodes) where we did an alias switch and still queried the old data from the old index for a couple of minutes before we got the new one. There was no load on the cluster during that time. Our indices have about 200k documents and are roughly 200 MB in size. Each index has one primary shard and two replicas.
We switched the index behind the alias to the newly build index and found out that we only got the new data after about 1-2 minutes.
Our theory is that the alias was not immediate and took some time (for whatever reason).
Can somebody explain in a bit more detail what happens when the alias is switched to a new index?