DataZip Interview Experience – SDE 2 (Golang)

📅 Round 1: DSA + Golang Fundamentals
Topics Discussed:
🔹 Questions based on past projects
🔹 Golang-specific concurrency concepts:

What is a WaitGroup and how does it manage goroutine lifecycle?

Difference between Concurrency vs Parallelism

What is the Worker Pool Pattern in Go?
→ Common concurrency pattern where multiple goroutines (workers) pull tasks from a shared job queue for efficient task distribution

What is the purpose of a done channel and how it signals goroutines to stop?

🧠 Coding Questions:
Q1: Word Transformation
Convert one word into another using minimum operations.
Operations allowed:

• Add a character
• Replace a character
• Delete a character

⏱ Time: 20 minutes

Q2: Flatten Nested JSON
Given a deeply nested JSON payload, return a flattened version without any nesting.
⏱ Time: 15 minutes

📅 Round 2: Internal Team (Goroutines + Go LLD)
🧩 Question 1: Concurrent Scheduler
Problem Context:

• A scheduler needs to execute N SQL queries concurrently
• System constraint: Warehouse crashes if more than 5 queries are run at once
• Max memory usage: 16 GB

✅ Expected:

• Run at most 5 queries in parallel
• Ensure efficient and safe execution using goroutines
• Each query should be executed via a function like: Execute(query) → prints result

🧩 Question 2: Document Service (Low-Level Design)
Requirements:

• Users can create documents (default: private)

• Owner can:

  • Edit the document
  • Grant access to specific users

• A document can also be marked as public

• Implement logic for:

  • Read
  • Write
  • Access control

❌ Result: Rejected in Round 2