In this service, the hashtable will be maintained in memory. In that case if our service will restart, then we will miss the hashtable. One more clarification will this will a global memory or system memory?

I’m confused about this as well. I assume the solution suggests we keep the data in the DB as well as the hashtable in memory. However, I don’t know how can we keep this hashtable in-sync if we have multiple app servers running at the same time.