AWS Interview Questions

Grant identities only the permissions they need for their task, nothing more. Prefer roles with temporary credentials over long-lived access keys, and avoid using the root user.

Elastic Compute Cloud provides resizable virtual servers. You choose an instance type, AMI, storage and security groups, and pay for the time instances run.

Simple Storage Service is object storage for files of any size, organised in buckets, with very high durability, versioning, lifecycle rules and multiple storage classes.

Security groups are stateful firewalls attached to instances that allow rules only. Network ACLs are stateless, apply at the subnet level and support allow and deny rules.

Amazon Web Services is a cloud platform offering compute (EC2, Lambda, ECS), storage (S3, EBS), databases (RDS, DynamoDB), networking (VPC, Route 53, CloudFront), security (IAM, KMS) and DevOps tools, billed per use.

A Region is a geographic area with several isolated Availability Zones (one or more datacentres each). Spreading across AZs gives high availability. Edge locations are separate points of presence used by CloudFront and Route 53 to serve users with low latency.

Users are long-term identities for people, groups attach permissions to many users, roles are assumed temporarily by services, apps or federated users, and policies are JSON documents that allow or deny actions on resources.

A template for an EC2 instance: the operating system, installed software and configuration. You launch instances from AMIs, and you can create your own “golden” AMI so new instances start ready to run.

Standard for frequent access, Intelligent-Tiering for unknown patterns, Standard-IA and One Zone-IA for infrequent access, and Glacier Instant/Flexible/Deep Archive for archives. Lifecycle rules move objects between classes automatically.

Upload the build to a private S3 bucket and serve it through CloudFront with Origin Access Control, HTTPS, caching, and an error-response rule that returns index.html for client-side routes.

RDS is a managed relational database (MySQL, PostgreSQL, SQL Server) with SQL and joins. DynamoDB is a serverless key-value/document database with single-digit-millisecond latency at any scale, designed around access patterns.

Serverless functions triggered by events, billed per request and duration. Limits include a 15-minute maximum runtime, memory caps, cold starts and statelessness.

A Virtual Private Cloud is your isolated network in AWS. Public subnets route to an internet gateway; private subnets do not and reach the internet (for updates) through a NAT gateway.

A managed relational database service for SQL Server, PostgreSQL, MySQL, MariaDB and Oracle (Aurora is AWS’s own engine). It handles provisioning, patching, automated backups, Multi-AZ failover and read replicas.

Start from access patterns, not entities. Choose a partition key with high cardinality to spread load, add a sort key for range queries, and use global secondary indexes for other patterns. Avoid scans in hot paths.

It is a managed front door for APIs: routing to Lambda, HTTP backends or AWS services, with authorisation (IAM, Cognito, JWT), throttling, CORS, request validation, stages and custom domains.

It is AWS’s DNS service. Besides simple records and alias records for AWS resources, it supports weighted, latency-based, failover, geolocation and multivalue routing with health checks.

AWS’s content delivery network. It caches content at edge locations close to users, terminates HTTPS, can sit in front of S3, load balancers or API Gateway, and supports origin access control so S3 buckets stay private.

AWS’s monitoring service: metrics, logs (CloudWatch Logs with Logs Insights queries), alarms that trigger notifications or scaling, dashboards and X-Ray/Application Signals for tracing.

Store them in Secrets Manager (with automatic rotation for databases) or SSM Parameter Store, grant the app’s IAM role permission to read only those secrets, and fetch them at startup or through the ECS/Lambda integrations.

An Application Load Balancer distributes traffic across healthy targets. An Auto Scaling group adds or removes instances based on metrics or schedules and registers them with the load balancer automatically.

AWS’s infrastructure-as-code service: you declare resources in YAML/JSON templates and CloudFormation creates, updates and deletes them as a stack, with change sets and drift detection.

Right-size instances, use Savings Plans or Reserved Instances for steady load and Spot for flexible work, apply S3 lifecycle policies, delete idle resources, use Cost Explorer and budgets, and tag everything.

ECS is AWS’s own container orchestrator. With Fargate you run tasks without managing servers; with the EC2 launch type you manage the instances. EKS is managed Kubernetes — portable and powerful, but more to operate.

CodePipeline triggers on a commit, CodeBuild runs buildspec.yml to test and build a container image pushed to ECR, and a deploy stage updates ECS (with CodeDeploy blue/green) or a CloudFormation stack, with manual approval before production.

1version: 0.2
2phases:
3  build:
4    commands:
5      - dotnet test
6      - docker build -t $REPO_URI:$CODEBUILD_RESOLVED_SOURCE_VERSION .
7  post_build:
8    commands:
9      - docker push $REPO_URI:$CODEBUILD_RESOLVED_SOURCE_VERSION

Combining managed services so you run no servers: API Gateway + Lambda for compute, DynamoDB for data, S3 for files, SQS/SNS/EventBridge for events and Step Functions for workflows. You pay per request and scale automatically.

Options include Elastic Beanstalk for a simple managed setup, ECS Fargate with an image in ECR behind an Application Load Balancer, App Runner for a quick container service, or Lambda with the ASP.NET Core hosting package. Use RDS for SQL Server and Secrets Manager for credentials.