what are the things that we need to consider for better application performance
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Which things are the slowest?
That's really the key. There's an old adage you'll find repeated over and over: "Premature optimization is the root of all evil."
If you have 2 nodes in the same PM that run for 10 seconds and 120 seconds, I don't care if you shave half the time of the 10 second one, not really. See if you can shave off even 10 % from the big one, and it will be better than making the small one completely free.
Determine how far upstream and how far downstream the problems are. If it involves a DB query, compare the time the DB portion takes to the time the Appian portion takes. If they're roughly the same, you've got a database problem. If the DB is fast in comparison, you've got an application problem. Always gather as little data as possible, filter as many rows as possible, return as few columns as possible. Learn explain plans.
Run your health check and within reason do what it says. Always remember to think about the reason why a best practice rather than blindly doing it. The first is wisdom; the second is cargo-cult.