PhonePe Machine Coding Round..What's the best way to implement it on production systems?

Coding Round

Questions: You need to design a system that is able to track pending entities. An entity is identified using a unique ID and a list of hierarchical tags. There are 3 parts to this problem statement: startTracking, endTracking, and getCounts.

• startTracking:

  void startTracking(Integer id, List hierarchicalTags);

  • id = Identifier of the entity
  • hierarchicalTags = Tags that are properties of the entity. These tags are hierarchical in nature.

• stopTracking:

  void stopTracking(Integer id);

  • id = Identifier of the transaction

• getCounts:

  Integer getCounts(List tags);

  • tags = a hierarchy of tags, for which counts are to be retrieved

Sample Usage:

startTracking(1112, ["UPI", "Karnataka", "Bangalore"]);
startTracking(2451, ["UPI", "Karnataka", "Mysore"]);
startTracking(3421, ["UPI", "Rajasthan", "Jaipur"]);
startTracking(1221, ["Wallet", "Karnataka", "Bangalore"]);

getCounts(["UPI"]); // Output: 3
getCounts(["UPI", "Karnataka"]); // Output: 2
getCounts(["UPI", "Karnataka", "Bangalore"]); // Output: 1
getCounts(["Bangalore"]); // Output: 0

startTracking(4221, ["Wallet", "Karnataka", "Bangalore"]);
stopTracking(1112);
stopTracking(2451);

getCounts(["UPI"]); // Output: 1
getCounts(["Wallet"]); // Output: 2
getCounts(["UPI", "Karnataka", "Bangalore"]); // Output: 0

Requirements:

• Implement the above with appropriate assumptions.
• Optimize for time/space complexity.
• Use in-memory data structures only.
• A working code is necessary for evaluation.