[fragmede]

Practice.

The interviewer knows you don't have personal experience building Dropbox, but a systems design interview question might be help me build Dropbox, for cats. Half of it is regurgitating information - what database would you use, Redis vs Mongodb vs Dynamodb vs Postgresql vs Spanner vs BigQuery vs BigTable vs Firebase, but more importantly, you need to show that you know the bigger concepts; relational vs key-value vs document store, and their trade-offs.

The interview is 45 minutes to see how you think, how you react to questions, how you behave as a human being, what happens when I throw in a curve ball. If I say your design is stupid, do you get mad and start yelling at me and call me names, or can you incorporate that feedback and adjust your design to accommodate a change in behavior.

Get to know the building blocks very well.

[3pm]

   "Half of it is regurgitating"
   "how you behave as a human being, what happens when I throw in a curve ball."

So it's half hazing, half theatrical performance?

[zer0sand0nes]

The problem is that for senior+ interviews, you need to know things like cold starts, consistent hashing, dealing with different invalidations techniques for the cache, etc - the combinations seem infinite

[fragmede]

There's a lot of stuff to know! Senior+ isn't called that because some rando can memorize a couple of things in 5 minutes and ace the interview. It takes years to learn tons everything and get an intuition for things, and even then there's a bunch you still won't know.

The systems design interview is in knowing enough of the building blocks and being smart enough to put them together, and being able to discuss why put them together that way. There's no right answer, using a relational database to ingest log messages from a service is an acceptable answer to the right question, but you have to be able to sit there and explain the tradeoffs being made and when you would and wouldn't want to do that.

As you've noted, studying the questions won't help unless you memorize enough of the questions and get lucky. So get to know enough of the building blocks well so you can come up with a combination of them that's reasonable. All systems have tradeoffs, what's the optimal, least-bad solution? What are the considerations you're optimizing for. The system you'd build for a FAANG isn't the same system you'd build for a VC-funded company, isn't the same one you'd build for a boot-strapped company.