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7.1 Serverless Architecture Patterns

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AWS Solutions Architect Associate SAA-C03

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1 Introduction

About the AWS Solutions Architect Associate (SAA-C03) Exam Study Strategies and Exam Tips for SAA-C03 The AWS Well-Architected Framework

2 Domain 1: Design Secure Architectures (30%)

1.1 IAM Fundamentals — Users, Groups, Roles, and Policies 1.2 AWS Organizations, SCPs, and Multi-Account Strategy 1.3 VPC Security — Security Groups, NACLs, and VPC Endpoints 1.4 Encryption, KMS, and Secrets Management 1.5 AWS WAF, Shield, and Network Firewall 1.6 GuardDuty, Inspector, Macie, and Security Hub 1.7 The Shared Responsibility Model for Solutions Architects 1.8 Data Protection, Compliance, and Audit Services

3 Domain 2: Design Resilient Architectures (26%)

2.1 Elastic Load Balancing (ELB) — ALB, NLB, and GWLB 2.2 EC2 Auto Scaling — Dynamic, Predictive, and Scheduled 2.3 Multi-AZ and Multi-Region Architectures 2.4 Disaster Recovery Strategies — RTO and RPO 2.5 Decoupling with SQS, SNS, and EventBridge 2.6 AWS Step Functions and Workflow Orchestration

4 Domain 3: Design High-Performing Architectures (24%)

3.1 EC2 Instance Types, Purchasing Options, and Placement Groups 3.2 Lambda, Serverless Compute, and Container Services 3.3 Amazon S3 - Storage Classes, Lifecycle, and Performance 3.4 Block and File Storage - EBS, EFS, and FSx 3.5 Database Services - RDS, Aurora, DynamoDB, and More 3.6 CloudFront, Route 53, and Global Accelerator 3.7 Data Ingestion and Transformation - Kinesis, Glue, and EMR

5 Domain 4: Design Cost-Optimized Architectures (20%)

4.1 Compute Cost Optimization — Right-Sizing, RIs, Savings Plans, and Spot 4.2 Storage Cost Optimization — S3 Tiers, EBS, and Data Transfer 4.3 Database Cost Optimization 4.4 AWS Cost Management and Monitoring Tools

6 VPC and Networking Deep Dive

5.1 VPC Architecture — Subnets, Route Tables, and Gateways 5.2 VPC Connectivity — Peering, Transit Gateway, and Direct Connect 5.3 Amazon API Gateway 5.4 CloudFormation and Infrastructure as Code 5.5 AWS PrivateLink and Endpoint Services

7 Migration, Transfer, and Hybrid Services

6.1 The 7 Rs of Cloud Migration 6.2 AWS Snow Family — Snowball Edge Devices 6.3 CloudWatch, CloudTrail, and AWS Config 6.4 Amazon Cognito and Identity Federation 6.5 AWS DataSync and Transfer Family

8 Serverless Architecture and Application Services

7.1 Serverless Architecture Patterns 7.2 Advanced SQS Patterns — DLQ, Backpressure, and FIFO 7.3 Analytics Services — Athena, OpenSearch, and QuickSight 7.4 Container Orchestration — ECS, EKS, and ECR

9 Advanced Topics and Exam Scenarios

8.1 Advanced IAM — Permission Boundaries, Federation, and Cross-Account 8.2 Caching Strategies and ElastiCache Patterns 8.3 Hybrid Architecture — DNS, Storage, and Compute 8.4 SAA-C03 Scenario Practice — Putting It All Together

7.1 Serverless Architecture Patterns

Key Takeaways Explain This Topic AI

The canonical serverless stack is API Gateway (HTTP front door) to AWS Lambda (compute) to DynamoDB or S3 (storage); add SQS for async buffering, Step Functions for orchestration, and EventBridge for event routing.

AWS Lambda has limits the exam tests: 15-minute max timeout for standard functions, 128 MB to 10,240 MB memory, up to 10 GB of /tmp ephemeral storage, and a 6 MB synchronous payload (1 MB async).

Serverless scales from zero and bills per invocation, making it ideal for spiky or unpredictable traffic; at high steady-state volume, EC2 or Fargate with Savings Plans can be cheaper.

Pick async (event source maps, SQS, SNS) for decoupling and retry safety; pick sync (API Gateway proxy) only when the caller must wait for a result within the 29-second API Gateway integration timeout.

Lambda@Edge and CloudFront Functions push serverless logic to edge locations for sub-millisecond request rewriting and header manipulation close to users.

Last updated: October 2026

What "Serverless" Means on the SAA-C03 Exam

On the AWS Certified Solutions Architect Associate (SAA-C03) exam, "serverless" is a design constraint, not a marketing word. When a question says minimize operational overhead , no servers to manage , or scale to zero , the answer is almost always a fully managed stack: API Gateway for the HTTP front door, AWS Lambda for compute, and DynamoDB or Amazon S3 for storage.

A service qualifies as serverless when it meets four tests at once: no instance provisioning, automatic per-request scaling, pay-only-when-running billing, and built-in multi-Availability-Zone (multi-AZ) redundancy. EC2, RDS, and self-managed ECS on EC2 all fail at least one test.

  • Characteristic Serverless behavior Exam trigger phrase
  • No server management AWS owns the OS and patching "reduce operational burden"
  • Auto-scaling Zero to thousands of concurrent executions "unpredictable / spiky traffic"
  • Pay-per-use Billed per invocation + GB-second "pay only for what you use"
  • Built-in HA Spans multiple AZs automatically "highly available without extra config"

Lambda Limits You Must Memorize

The exam loves to disqualify Lambda by quietly violating a limit. A batch job that runs 30 minutes cannot use a standard Lambda function (15-minute cap) and must move to AWS Fargate , AWS Batch , or Step Functions with Activity workers.

Limit Value Architecture implication

Max timeout 15 minutes (standard functions; Lambda Managed Instances allow up to 90 minutes for asynchronous and event-source-mapping invocations) Long jobs go to Fargate / Batch / Step Functions

  • Memory 128 MB to 10,240 MB (CPU scales with memory) More memory also buys more vCPU
  • /tmp ephemeral storage 512 MB default, up to 10 GB Large file processing needs the bump
  • Deployment package 50 MB zipped, 250 MB unzipped, 10 GB container image Big dependencies use container images
  • Synchronous payload 6 MB Large bodies go to S3, pass the key
  • Concurrency 1,000 default per Region (soft) Use reserved / provisioned concurrency

Worked example: A team reports cold starts spiking p99 latency on a checkout API. The fix is provisioned concurrency , which keeps a pool of initialized environments warm; reserved concurrency only caps the ceiling, it does not pre-warm.

The Six Patterns Tested Repeatedly

Most serverless questions map to one of these flows. Memorize the trigger words on the right.

Synchronous REST API: Client to API Gateway to Lambda to DynamoDB . Trigger: "CRUD API, mobile backend." Remember the 29-second API Gateway integration timeout, the real reason long work cannot be synchronous.

Event-driven processing: S3 PutObject event to Lambda to DynamoDB + SNS . Trigger: "process each uploaded image/document."

Async with a buffer: API Gateway to SQS to Lambda . Trigger: "smooth out bursts, decouple, survive downstream outages."

Scheduled task: EventBridge Scheduler (cron) to Lambda . Trigger: "nightly cleanup, report generation."

Streaming: Kinesis Data Streams to Lambda then Firehose to S3/Redshift . Trigger: "real-time IoT/clickstream analytics."

Fan-out: SNS topic to multiple SQS queues to independent Lambdas . Trigger: "one event must trigger several independent workflows."

Serverless vs. Container vs. EC2

  • Aspect Serverless (Lambda) Fargate EC2
  • Ops overhead None Low High (patching)
  • Scaling Per request, to zero Per task Auto Scaling groups
  • Idle cost Zero Per running task Always-on
  • Max duration 15 min Unlimited Unlimited
  • Cold starts Yes Minor None
  • Best for Spiky, event-driven Steady containers Legacy, GPU, licensing

Common trap: "steady 24/7 high-throughput workload, minimize cost" is NOT a serverless answer. Constant Lambda invocations cost more than a Fargate or EC2 fleet on a Savings Plan. Reserve serverless for variable load. Conversely, "traffic from 0 to 10,000 requests per minute, unknown pattern" is serverless because only Lambda scales from zero with no idle charge.

Orchestration, Events, and Glue Services

Real serverless systems stitch several managed services together, and the exam expects you to know which glue service solves which coupling problem.

AWS Step Functions orchestrates multi-step workflows as a state machine with built-in retries, error catching, and parallel branches. Choose it when a question describes a multi-stage process with conditional logic, human approval steps, or wait states that exceed Lambda's 15-minute limit. Standard workflows run up to a year; Express workflows handle high-volume, short-duration event processing.

Amazon EventBridge is the event bus for routing and filtering events between AWS services and software-as-a-service (SaaS) partners. It is the answer for "decouple producers from consumers with content-based routing" and for cron-style schedules via EventBridge Scheduler.

Amazon SNS is pub/sub push messaging; Amazon SQS is pull-based buffering. Combining them (SNS to SQS) gives durable fan-out where each subscriber gets its own retry buffer.

AWS AppSync provides a managed GraphQL API with real-time subscriptions, useful when a mobile client needs to subscribe to live data changes.

  • Coupling problem Service to reach for
  • Multi-step workflow with retries Step Functions
  • Route/filter events by content EventBridge
  • Buffer bursts, absorb downstream outage SQS
  • Push one message to many subscribers SNS

Idempotency note: because Lambda event sources can deliver a message more than once (at-least-once delivery from SQS, S3, and SNS), exam-grade serverless designs make handlers idempotent, often by recording a processed-message key in DynamoDB before acting.