AWS Service Comparisons

AWS certification exams frequently test "which service to use when." These comparisons summarize easily-confused service pairs (and trios) in tables, with decision criteria and exam-focused points.

Comparisons

Computing

EC2 vs Lambda

EC2 gives you a virtual server you manage yourself; Lambda is an event-driven, serverless execution environment. The core difference is "always running" vs "runs only when triggered."

Networking

ALB vs NLB

Both are Elastic Load Balancing (ELB) load balancers, but ALB operates at Layer 7 (HTTP/HTTPS) with content-aware routing, while NLB operates at Layer 4 (TCP/UDP) for ultra-high-performance routing.

Storage

S3 Storage Classes

S3 offers multiple storage classes based on access frequency. The less frequently you access data, the lower the storage cost, but minimum storage duration, retrieval fees, and retrieval time all increase.

Database

RDS vs Aurora vs DynamoDB

RDS and Aurora are both relational (SQL) databases, but Aurora is an AWS-built engine optimized for high availability and throughput. DynamoDB is a schemaless NoSQL database built for massive scale and low latency.

Application Integration

SQS vs SNS vs EventBridge

SQS is a polling-based queue for one-to-one delivery. SNS is a push-based pub/sub service for one-to-many fan-out. EventBridge is an event bus that flexibly routes events to multiple targets based on rules.

Networking

VPC Endpoint vs NAT Gateway

A VPC endpoint privately connects your VPC to AWS services. A NAT Gateway provides outbound internet access from private subnets. They serve different purposes and are often used together in the same VPC.

Networking

CloudFront vs Global Accelerator

CloudFront is a Layer 7 CDN that caches content at edge locations. Global Accelerator is a Layer 4 service that optimizes routing over the AWS global network without caching.

Containers

ECS vs EKS vs Fargate

ECS and EKS are alternatives along the "which container orchestrator" axis. Fargate is a serverless launch type that runs underneath either one — not a third parallel option. Understanding this distinction is the key to this comparison.

Security / IAM

IAM User vs Role vs Policy

IAM users and IAM roles are both principals representing "who or what" accesses AWS, but differ in the nature of their credentials. An IAM policy is the permission document attached to either one, defining "what is allowed."

Storage

Snapshot vs AMI vs AWS Backup

An EBS snapshot is a volume-level backup. An AMI is a launch template for instances (which internally uses snapshots). AWS Backup is a centralized backup management service spanning multiple AWS services.

References

Last updated: 2026-09-06

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