Razorpay Interview Questions & Answers 2026

Smart routing across PG providers (Visa/Mastercard, RuPay, UPI, wallets) for highest success rate and lowest cost. Components: rule engine, A/B testing framework, real-time success rate tracking, fallback logic, retry mechanism. Bank-specific success rates updated minute-by-minute. Critical for Razorpay's value prop.

Stream processing on transactions (Kafka + Flink). Features: velocity (transactions/hour), amount anomaly, location mismatch, device fingerprint, behavioral patterns. ML model (Random Forest or Neural Network) gives risk score. Rules engine for hard blocks. Feedback loop: false positives improve model. Sub-second decision latency.

Reliable webhook delivery to merchants with retries. Components: event publisher, queue (Kafka), webhook dispatcher, retry queue with exponential backoff, dead letter queue, signature generation (HMAC), delivery logs. Handle: merchant downtime, slow endpoints, idempotency. Scale: millions of events/day.

Razorpay is PCI-DSS Level 1 certified. Card data never touches merchant servers - tokenized via Razorpay JS SDK. Network isolation, encryption at rest (AES-256) and in transit (TLS 1.3), key management (HSM), regular pen testing, access controls (role-based), audit logging, vulnerability scanning. Annual PCI audit by QSA.

Track timestamps of requests in a queue (or sorted set in Redis). On new request: remove timestamps older than window, check if count < limit, add new timestamp. For approximate version: use buckets (e.g., 1-sec buckets in 1-minute window). Distributed: use Redis with Lua script for atomicity. Time O(log n) with sorted set.

Approach 1: Get lengths, advance longer list pointer by diff, then move both together until they meet. Time O(n+m), Space O(1). Approach 2: Two pointers - when each reaches end, redirect to other's head; they'll meet at intersection (or both null if no intersection). Elegant O(1) space.

Razorpay focuses on businesses (B2B) while Paytm/PhonePe focus more on consumers. Mention Razorpay's developer-first approach (best APIs, docs), neobanking products (RazorpayX, Capital), strong engineering culture, transparent pricing. Founded by IIT Roorkee alumni, profitable scaling, valued $7.5B. Smaller than competitors means more impact and ownership.

Use STAR method. Describe context (technical problem, constraints), options considered with tradeoffs (e.g., monolith vs microservices, SQL vs NoSQL), decision criteria, decision made, implementation challenges, outcome with metrics. Razorpay values strong technical judgment.