Round 1 -> Concurrency and multi-threading

Implement a concurrent in meomry feature flag system. where each feature might have a difference refresh interval. there might be diffrent sources for flags (all execlusive).

I followed clean architecture. stored feature flags in hash map. before returning check if the TTL is expired. then reload the flag.
one more thing to think about here is performance due to granluar lock. Locking entire hashmap might not be efficient.

Round 2 -> Implement a payment execution platform like razorpay. Your service should not have latency higher than 5 secs.