Scaling Reads medium
In the 'Cache-Aside' pattern, what happens when the application requests data that is NOT in the cache?
- A The application queries the DB, gets the result, writes it to the Cache, and then returns it.
- B The Cache automatically queries the DB.
- C The application returns an error.
- D The DB pushes the data to the Cache.
Answer: A. The application queries the DB, gets the result, writes it to the Cache, and then returns it.
In Cache-Aside, the code is responsible for loading data. Read-Through (Option B) pushes this logic into the cache provider/library itself.
One system design question a day, with spaced repetition so the ones you miss come back.
Get the appRelated questions
- In a caching system, what is a 'Cache Miss'?
- Why is `SELECT * FROM Users` generally discouraged in high-performance applications compared to `SELECT name, email FROM Users`?
- You have users all over the world downloading large images from your server in New York. Users in Australia complain it is slow. What solves this?
- What is the main downside of reading from a Read Replica instead of the Primary database?
- You have maximized the RAM on your single database server, but it's still too slow. You decide to add 10 more servers to share the load. What is this called?
- You have 5 Read Replicas. How does the application know which one to ask for data?