DevOps & CloudInterview questions and answers

EC2 (Elastic Compute Cloud) is AWS's virtual server service — you launch instances (VMs) of various sizes and operating systems on demand. It's the foundational compute primitive on AWS, used directly or as the underlying engine for many higher-level services (ECS, EKS, Beanstalk).

Categorized by workload: t (burstable, general-purpose), m (general), c (compute-optimized), r (memory-optimized), g/p (GPU for ML/graphics), i (storage-optimized with NVMe), x (extreme memory). Each has generations (m5, m6, m7); newer is usually cheaper per unit of performance.

S3 (Simple Storage Service) is AWS's object storage — virtually unlimited capacity, 11 nines of durability, with versioning, lifecycle rules, server-side encryption, and event triggers. Used for static assets, backups, data lakes, ML training data, and as a building block for almost every AWS service.

Standard (default), Intelligent-Tiering (auto-moves between tiers based on access), Standard-IA (infrequent access, cheaper but with retrieval fees), One Zone-IA (cheaper, single AZ), Glacier Instant/Flexible/Deep Archive (cold, costs less but slow to retrieve). Pick per access pattern.

IAM (Identity and Access Management) controls who can do what on which resources in AWS. Core concepts: users, groups, roles (assumable identities for services), policies (JSON documents granting permissions). Get IAM right and most security follows; get it wrong and nothing else matters.