Interview Q&A / AWS & Cloud

1. What is Amazon S3 and what are its storage classes?

   S3 is AWS's object storage. You store files as objects inside buckets and access them by key over HTTPS. Storage classes trade storage cost against access speed and retrieval cost, from S3 Standard for frequently used data to the Glacier classes for archives you rarely read.

   BeginnerIn-depth4 min read
2. What is the difference between an AWS Region and an Availability Zone?

   A Region is a separate geographic area, like Mumbai, with its own set of data centres. An Availability Zone is one or more isolated data centres inside a Region, with its own power and networking. You spread an app across AZs to survive a data-centre failure, and across Regions to survive a whole-area outage or to be closer to users.

   BeginnerIn-depth3 min read
3. What is the difference between EC2 and Lambda, and when would you pick each?

   EC2 gives you a virtual server that you run and manage, billed while it is running. Lambda runs your function only when an event arrives, scales automatically and bills per request and execution time. Pick Lambda for short, spiky, event-driven work; pick EC2 for long-running, steady or highly customised workloads.

   BeginnerIn-depth4 min read
4. What is the difference between IAM users, groups, roles and policies in AWS?

   A user is an identity for one person or app with long-term credentials. A group is a set of users that share permissions. A role is an identity that anyone or anything trusted can assume to get temporary credentials. A policy is the JSON document that says what is allowed or denied. Grant only the permissions needed, which is least privilege.

   BeginnerIn-depth4 min read