3. Not being specific about any technologies. Instead of using a "SQL Database" and a "cache", just say "PostgreSQL" and "Redis". It's an interview, if you're not specific, I will start thinking you don't have any experience with Redis or Postgres. If you really don't have any, I will find out anyway.
- when you pick specific technology, you also have to defend why this one specifically. For ex, why redis and not memcache or why only postgres and not redshift..
If you keep it at sql and no-sql, you can easily defend the answer and control the interview
Like if the design depends on modifying two keys atomically, a transaction is required. Some KV stores have that ability, some don’t. Do you need the keys to be in the same shard now? What kind of persistence is required here?
Redis and Memcache are quite different where the rubber meets the road. Gotta know what you’re talking about, don’t handwave over the details.
Strong no.
From the outside, it all feels random: unless you know the rules the interview is playing by, you can easily make a mistake. Each place has a different interview script and priorities.
(This is the same advice I give people when I'm coaching them for FAA oral exams, incidentally. People really have a hard time listening to a question and answering the actual question.)