HDFC - Golang Backend Engineer Interview Experience

Recently attended the interview process for HDFC - Golang Backend Engineer. Below are the questions asked across all the rounds.

Experience: ~4 Years (Golang Backend)

Screening Round

Golang

• What are goroutines?
• How are goroutines different from OS threads?
• What are channels?
• How do channels work internally?
• How does Go manage memory?
• What happens when a buffered channel becomes full?
• Advantages of Go over Java or Node.js for backend systems.

APIs

• Difference between REST and gRPC APIs.
• Are REST APIs stateful or stateless?
• Difference between GraphQL and REST APIs.
• Difference between JWT and session-based authentication.

System Design & Backend

• What is Docker?
• What is Kubernetes?
• What are message queues, and when are they used?
• Difference between SQL and NoSQL databases.
• In which scenarios would you use an SQL database?
• In which scenarios would you use a NoSQL database?
• Difference between Monolith and Microservices.
• When would you choose a Monolith over Microservices?
• When would you choose Microservices architecture?
• What is backpressure?
• What are the different cache write strategies?
• What are the different cache eviction policies?
• How would you prevent cache stampede?

AI

• As a senior engineer, if you are asked to work with a new framework or unfamiliar technology, how would you leverage AI to learn and deliver efficiently?

Coding Question 1

Given an array of integers, implement a solution using multiple goroutines to find all unique sums generated by adding every pair of numbers.

Example

Input:
[1, 3, 6, 8]

Possible sums:
1+3=4
1+6=7
1+8=9
3+6=9
3+8=11
6+8=14

Output:
4 7 9 11 14

Constraints

• Use multiple goroutines.
• The implementation should be synchronous.
• Duplicate sums should appear only once.

Coding Question 2

Write a program to print numbers from 0 to 9 using two separate goroutines.

Requirements:

• One goroutine should print even numbers.
• One goroutine should print odd numbers.
• The output should be synchronized so that the numbers are printed in order.

Expected Output

0 1 2 3 4 5 6 7 8 9

Technical Round

Golang

• What is bounded concurrency? How is it implemented using worker pools?
• How would you allocate the number of CPU cores to a Go program (GOMAXPROCS)?
• What is the order of execution when multiple defer statements are used?
• Explain Go's garbage collector.
• Which algorithm does Go's garbage collector use?
• What are the latest improvements in Go 1.26 (e.g., Green Tea GC, SwissMap, encoding/json/v2)?
• Difference between:
  • Single quotes (' ')
  • Double quotes (" ")
  • Backticks (` `)

Maps

• Declare a global map.
• Why do we use make()?
• How do you check whether a key exists in a map?
• What hashing algorithm is used internally by Go maps?

Environment

• How do you get all environment variables in Go?
• Difference between GOROOT and GOPATH.

OOP & Design Principles

• Explain Object-Oriented Programming concepts with Go implementations.
• Why do we use pointer receivers instead of value receivers?
• Explain interfaces in Go.
• What benefits do interfaces provide?
• Write an example demonstrating polymorphism using interfaces.
• Explain the SOLID principles.

Microservices

• What is the SAGA pattern?
• What is the Strangler Fig pattern?
• Difference between Orchestration and Choreography.
• What is a Circuit Breaker?
• Implement a Circuit Breaker in Go.

AI

• What exposure do you have to AI?
• How are voice agents implemented? (STT → VAD → LLM → TTS)
• Where is the data stored? (PostgreSQL + pgvector)
• What latency requirements do you target?
• How do you manage concurrency and scaling?
• Are you using RAG? Explain how it works.

Coding Questions

1. Panic Recovery

• Write a panic recovery block.
• Explain the lifecycle of panic, defer, and recover.

2. TTL Cache

• Design and implement a TTL Cache with an HTTP server.

3. Concurrency

• Write a program to print odd and even numbers alternately using two goroutines.

4. Interfaces

• Explain interfaces in Go.
• Write a program demonstrating polymorphism using interfaces.

Final Round

Mostly discussion-based.

Topics covered:

• Previous company experience
• Projects
• Golang expertise
• Previously faced Techincal problems
• Backend architecture
• Skills and future goals
• Concurrency Patterns

Overall Focus Areas

If you're preparing for the HDFC Golang Backend Engineer role, make sure you're comfortable with:

• Go internals (goroutines, scheduler, channels, memory management, GC, maps)
• Concurrency patterns (worker pools, bounded concurrency, synchronization)
• REST, gRPC, GraphQL
• Authentication & Authorization (JWT, OAuth, Sessions)
• SQL vs NoSQL and database optimization
• Docker & Kubernetes
• Caching strategies, eviction policies, and cache stampede prevention
• Message queues and backpressure
• Microservices patterns (SAGA, Strangler Fig, Orchestration vs Choreography)
• Circuit Breaker pattern
• Go interfaces, OOP concepts, and SOLID principles
• AI fundamentals (LLMs, RAG, voice agents, vector databases)
• Coding using goroutines, channels, panic recovery, and cache design
• Behavioral and project-based discussions

Overall, the interview was heavily focused on Go internals, concurrency, backend architecture, microservices, AI fundamentals, and practical problem-solving.

Good luck to everyone preparing! 🚀