Cloud Technology and Services
Core Service Categories
Candidates must know the major AWS service families and their use cases. Compute: EC2 (virtual servers), Lambda (serverless functions), ECS/EKS (containers), Elastic Beanstalk (PaaS). Storage: S3 (object), EBS (block for EC2), EFS (file), Glacier (archive). Databases: RDS (relational managed), DynamoDB (NoSQL), Redshift (data warehouse), Aurora (MySQL/PostgreSQL-compatible). Networking: VPC (isolated network), Route 53 (DNS), CloudFront (CDN), Direct Connect (dedicated network), API Gateway. Management: CloudWatch, CloudFormation (infrastructure as code), Systems Manager. Integration: SQS (queue), SNS (pub/sub), Kinesis (streaming).
Traps to Watch
A frequent trap is choosing EBS when the scenario requires shared storage across multiple instances: EBS is tied to one AZ and typically one instance, while EFS is shared and multi-AZ. Another is confusing S3 (object storage, unlimited) with EBS (block storage, sized). For databases, DynamoDB is serverless NoSQL with single-digit millisecond latency; Redshift is for analytics, not OLTP. CloudFront caches content at edge locations; it does not replace an ALB. Route 53 routing policies (latency, failover, geolocation) are often tested. Also, Lambda has a 15-minute execution limit; SQS standard queues are at-least-once, FIFO is exactly-once.
Worked Example / Rule of Thumb
A company needs to run a batch job that takes 2 hours. Lambda cannot run that long (15-minute limit), so use AWS Batch or EC2. Rule of thumb: if the workload is event-driven and short (<15 min), choose Lambda; if it is long-running or needs persistent compute, choose EC2/ECS/Batch.
Key Takeaways
- S3 = object; EBS = block (single AZ); EFS = shared file (multi-AZ).
- Lambda max runtime is 15 minutes; use Batch/EC2 for longer jobs.
- DynamoDB = serverless NoSQL; Redshift = analytics warehouse; RDS = managed relational.
- CloudFront = CDN; Route 53 = DNS with routing policies; VPC = isolated network.
- CloudFormation = infrastructure as code; SQS = queue; SNS = pub/sub.