AWS Interview Questions 2026

Design a distributed rate limiter that can handle 10M requests per second across multiple data centers. Discuss consistency tradeoffs, the choice between token bucket vs leaky bucket, and how you would handle clock skew across regions.

Design Amazon's recommendation engine (customers who bought X also bought Y). Cover: collaborative filtering vs content-based, item-item similarity at scale, real-time vs batch computation, and how you handle the cold-start problem for new products.

Explain Amazon's DynamoDB single-table design pattern. Why do you put multiple entity types in one table? Walk through a real example with access patterns, partition key / sort key design, and GSI usage.

What is the difference between an S3 bucket policy, IAM policy, and S3 ACL? Which takes precedence?

What is Lambda cold start and why does it happen? Name two concrete techniques to reduce its impact on a latency-sensitive API.

Explain your deployment workflow starting from code commit until production release. Cover feature branch → PR → CI → merge → staging deploy → smoke tests → canary/blue-green production deploy → monitoring and rollback plan.

Design a serverless ETL pipeline on AWS that processes files uploaded to S3 and loads them into Redshift.

A client's AWS bill has grown 40% in 6 months with no corresponding growth in usage. What are the first three things you would check?

Design Swiggy's real-time order tracking system. A customer should see their delivery agent's location update every 5 seconds on a map. Cover: location ingestion from agents, WebSocket vs SSE for pushing updates to clients, data store choices, and how you scale to 100k concurrent orders during peak hours.

Design Swiggy's notification system. When an order status changes (Confirmed, Picked Up, Arriving), send push notification, SMS, and in-app notification reliably with at-least-once delivery. Cover fan-out and handling inactive devices.

Design Zomato's surge pricing engine. When demand spikes (rain, IPL final), delivery fees increase automatically. Cover: demand signals, pricing formula, fairness constraints, A/B testing pricing strategies, and how to avoid customer backlash.

Design Uber's driver-rider matching system. How do you match the nearest available driver to a rider within 200ms at global scale? Cover: geospatial indexing (H3/S2), the dispatch algorithm, how you handle supply-demand imbalances, and what happens when a matched driver rejects the trip.

Design Stripe's webhook delivery system. Stripe sends millions of webhooks per day to customer endpoints that can be slow, down, or buggy. Cover: at-least-once delivery guarantees, retry with exponential backoff, ordering guarantees (or lack thereof), how to handle a customer endpoint that is down for 24h, and the dead-letter strategy.

Design a multi-tenant SaaS database architecture like Salesforce's. Thousands of enterprise customers share the same infrastructure but must never see each other's data. Compare silo (one DB per tenant), pool (shared DB, tenant_id column), and bridge models. Discuss query performance, schema customisation, and compliance isolation.

Design Adobe's document collaboration system (similar to Google Docs for PDFs). Multiple users can annotate and comment on a PDF simultaneously. Cover: conflict-free annotation merging, storing annotation deltas vs full snapshots, real-time sync via WebSockets, and how you export the final annotated PDF.

Design Adobe Sign (e-signature platform). A contract is sent to 5 signatories who must sign in a specific order. Cover: document integrity (hash verification), audit trail, legal compliance (e-SIGN Act), and what happens if a signatory refuses.

Design iCloud Photo Library — 2 billion photos synced across iPhone, iPad, and Mac. Cover: deduplication (perceptual hashing), delta sync (only changed chunks), offline-first with conflict resolution, and privacy — how Apple performs server-side processing without seeing unencrypted photos.

Design Netflix's video recommendation system. Netflix serves 250 million subscribers. How do you generate personalised top-10 rows for each user in real time? Cover: collaborative filtering, content-based signals, contextual signals (time of day, device), and how you handle the cold-start problem for new users.

Design Netflix's adaptive bitrate streaming (ABR) system. How does the client decide which video quality to stream second by second based on available bandwidth? Explain DASH vs HLS, the segment request pipeline, buffer-based rate adaptation algorithms, and CDN architecture.

Design Netflix's content delivery pipeline. A new movie is added. Walk through transcoding into 50+ formats, uploading to CDN edge nodes globally, and ensuring playback starts within 200ms for any device anywhere.

Explain Netflix's Chaos Engineering philosophy and the Simian Army. How do you design a system to be resilient to random instance failures, network partitions, and zone outages? Give a concrete example.

Design Netflix's A/B testing platform. Engineers run 100+ experiments simultaneously on different features. How do you assign users to buckets consistently, collect metrics, measure statistical significance, and avoid interaction effects?

Your RDS MySQL database is becoming a bottleneck. Read queries are slow. How do you scale it on AWS without re-architecting the entire application?

Design the video encoding pipeline that takes a raw uploaded file and produces multiple bitrate/resolution variants for adaptive streaming. How do you make this fault-tolerant and cost-efficient at scale?

Netflix popularized "chaos engineering" — explain what problem it actually solves that traditional testing doesn't, and how you would introduce it safely into a system that has never done it before.

Design Facebook Live - a system to stream live video from one user to potentially millions of concurrent viewers with low latency. Cover: ingest pipeline, transcoding, CDN edge caching, adaptive bitrate, and how you handle a celebrity going live.

Design Paytm's KYC (Know Your Customer) pipeline. Users must submit Aadhaar/PAN documents for verification. How do you store documents securely (encrypted at rest), verify them (ML + manual review), and handle status callbacks?

Design Confluence's page version history. Every edit creates a new version. Users can view any historical version and restore it. Cover: delta vs full-snapshot storage, efficient diff computation, and how you handle concurrent edits creating a branch.

Design Bitbucket's code review system (Pull Requests). Multiple reviewers comment on specific lines of code. The PR is mergeable when all reviewers approve. Cover: diff computation, inline comments anchored to code lines, and what happens when new commits invalidate existing comments.

Your application on EC2 experiences a spike to 10x normal traffic every Friday at 6 PM. How do you architect for this predictable load?

Your company needs 99.99% uptime for a critical web application. How do you architect a multi-region active-active setup on AWS?