Mid Level Interview Questions

1. Singleton, Young and old generation garbage collection, Make 2 HTTP request with completable future and merge 2 response. give some code to fix it
2. Redis related - is it persistent? 
3. master-slave Redis cluster - if data missed in master what it will return
4. different HTTP method and how it used?
5. what is the purpose of the OPTION method?
6. is restful API state-full or stateless? and why?
7. is singleton thread safe or not? how to make it threadsafe?
8. serialization? where it used?
9. if any class have 5 property and if they want to make 4 property serialized, how can I do it?

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• What is synchronization?
• Recursion related multiple issue understanding and related code optimization.
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