Why reading data on grafana takes time after restart

So whenever we restart influxdb, we notice that it takes quite a while for grafana to reconnect/read data from influxdb.(up to ~10m)

However, when it comes to writing data and accessing /health endpoint the DB is available within ~2-3 mins.

Why does the DB take a longer time to serve reads after the DB service/process is restarted?

Is it related to WAL flushing, but why does that affect read?

I think you answered your own question

Points in the WAL can be queried, and they persist through a system reboot. On process start, all points in the WAL must be flushed before the system accepts new writes.

I believed they’re flushed to accept new writes which is why querying the WAL is affected.