Let’s share this time Apple 26NG VO’s complete interview review. In summary, it was two rounds of pure technical skills. The pace was obviously fast, but the experience was actually good. Apple’s recent interview arrangements are indeed very clear between technical aspects and behavioral aspects. Both rounds are purely technical in-depth.
First round of VO: Timestamp Key-Value Store design
Design a timestamp-based key-value store that supports setting a value at a specific timestamp and querying for new values no greater than the given timestamp. Idea: Use a hash table to store the mapping of keys to (timestamp, value) lists. When setting the value, append it directly to the list; when querying, perform a binary search on the ordered timestamp list to find the last value that is not greater than the target timestamp. From medium to higher difficulty level, it’s okay.
Follow-up
1. If the amount of data is extremely large, how to optimize memory usage? This I give to students is to use compressed timestamps or archive old data periodically
2. How to support multi-threaded concurrent reading and writing? This uses ConcurrentHashMap and synchronized blocks, or assigns independent locks to each key.
3. How to design distributed time series storage? Sharding by key, each machine is responsible for part of the key, distributed through consistent hashing.
Second round of VO: Frequency stack design
Design a data structure that supports adding elements and querying the elements that appear most frequently
Idea: Use three core structures: a hash table to record the current frequency of elements, a hash table to record the element stack corresponding to each frequency, and a variable to record the current max frequency. When pushing, update the element frequency and add the element to the new frequency stack; when pop, pop the top element from the max frequency stack and update the frequency if the stack is empty.
Follow-up
1. Support deleting any element, maintaining bidirectional index, and updating frequency stack and element position.
2. Design a distributed version, shard by element hash, and global frequency statistics require cross-node coordination.
Overall feeling
In summary, Apple's technical style is very straightforward. The interviewer will not spend too much time laying out the background, nor will he deliberately set traps, but will follow your answers and ask questions layer by layer. Don’t panic if you’re not sure about the interview, we can provide VO one-to-one assistance , we are familiar with the high-frequency question types, answer ideas, and on-the-spot techniques from big companies. We have helped many students successfully get offers. You can contact us anytime if you need it.
