Signzy Software Engineer Interview: Rounds, Questions and Preparation

What the job involves

As a Software Engineer at an Indian SaaS or B2B product company, you will build and maintain features for cloud-based platforms used by businesses for payments, compliance, analytics, or workflow automation. Day to day, you will write backend or full-stack code, fix bugs, participate in code reviews, and collaborate with product and QA teams to ship reliable software. You will also work on APIs, databases, and integrations that power multi-tenant, scalable systems.

Role and Technical Knowledge

1. 1

   Explain how a REST API works and how you would design an endpoint for creating a new customer in a B2B SaaS platform.

   Cover HTTP methods, status codes, request/response JSON, authentication, and idempotency. Mention versioning and validation.

2. 2

   What is multi-tenancy in SaaS, and how would you ensure one tenant's data does not leak to another?

   Discuss tenant isolation strategies (shared DB with tenant ID, separate schemas, separate DBs) and enforce row-level security or query filters.

3. 3

   Given a scenario where a payment webhook is received twice, how would you ensure the transaction is not processed twice?

   Talk about idempotency keys, unique constraints, and storing event IDs. Mention retry logic and eventual consistency.

4. 4

   How would you design a simple notification service that sends emails and SMS to users of a B2B product?

   Cover queue-based architecture, third-party providers, retries, rate limiting, and logging. Mention template management and user preferences.

Practical Scenarios

1. 5

   You are asked to add a new feature to an existing codebase you have never seen. How do you approach it?

   Explain reading documentation, understanding existing patterns, writing tests, and making small incremental changes. Mention asking for help when stuck.

2. 6

   A production bug is reported: users cannot log in after a deployment. How do you debug and resolve it?

   Describe checking logs, recent changes, rollback options, and reproducing the issue. Mention communicating with the team and post-mortem.

3. 7

   Your team needs to integrate a third-party KYC API. What factors do you consider before writing code?

   Consider API rate limits, error handling, data privacy, fallback mechanisms, and testing with sandbox environments.

4. 8

   How would you optimize a slow SQL query that fetches customer transactions for a dashboard?

   Discuss indexing, query analysis with EXPLAIN, avoiding N+1 queries, caching, and pagination. Mention database normalization vs denormalization.

Behavioural and HR

1. 9

   Why do you want to work in a B2B SaaS product company like Signzy rather than a consumer tech company?

   Show understanding of B2B challenges: complex workflows, enterprise customers, compliance. Connect to your interest in building scalable, reliable systems.

2. 10

   Tell me about a time you worked in a team to complete a project. What was your role and how did you handle disagreements?

   Use STAR method. Highlight collaboration, communication, and how you resolved conflict constructively.

3. 11

   Describe a situation where you had to learn a new technology quickly for a project or hackathon.

   Focus on your learning process, resources used, and the outcome. Show adaptability and self-motivation.

4. 12

   Where do you see yourself in three years, and how does this role fit into your career goals?

   Align your growth with the company's needs: deepening technical skills, taking ownership, and contributing to product success. Avoid vague answers.

Coding and Problem Solving

1. 13

   Given an array of integers, find two numbers that add up to a target sum. Explain your approach and optimize it.

   Start with brute force O(n^2), then use hash map for O(n). Discuss edge cases and space-time trade-offs.

2. 14

   Write a function to detect if a linked list has a cycle. How would you find the starting node of the cycle?

   Use Floyd's cycle detection (tortoise and hare). Explain how to find the start after meeting point.

3. 15

   Design a class for a simple in-memory key-value store with expiration. What data structures would you use?

   Combine hash map with a priority queue or doubly linked list for TTL. Discuss thread safety and cleanup.

4. 16

   Given a string, find the longest substring without repeating characters. Walk through your solution.

   Use sliding window with a set or map to track characters. Explain time complexity O(n) and handle edge cases.