Technologies And Concepts: Cheat Sheet for Developer Associate (DVA-C02)

Exam Guide: Developer – Associate
Technologies And Concepts Cheat Sheet
📘 Cheat Sheet

1 | Services

Compute

Service What It Does Key Points Lambda Serverless Functions 15 min timeout, 10240 MB memory max, 1000 default concurrency EC2 Virtual Servers Instance profiles for IAM roles, user data for bootstrap ECS/Fargate Container Orchestration Task roles for IAM, Fargate = serverless containers Elastic Beanstalk PaaS Deployment .ebextensions for config, supports rolling/immutable/blue-green

Storage & Databases

Service What It Does Key Points DynamoDB NoSQL key-value Partition keys, GSI/LSI, query vs scan, DAX for caching S3 Object Storage SSE-S3/SSE-KMS/SSE-C, lifecycle policies, presigned URLs ElastiCache In-memory Cache Redis (complex types, persistence) vs Memcached (simple, multi-threaded) RDS Relational Database RDS Proxy for Lambda connection pooling, read replicas OpenSearch Search & Analytics Full-text search, log analytics

API & Integration

Service What It Does Key Points API Gateway REST/HTTP/WebSocket APIs Stages, authorizers, caching, request validation, throttling SQS Message Queue Standard (at-least-once) vs FIFO (exactly-once), visibility timeout, DLQ SNS Pub/sub messaging Fanout, filter policies, message attributes EventBridge Event Bus Pattern matching, content-based filtering, multiple targets Kinesis Real-time Streaming Shards, partition keys, parallelization factor Step Functions Workflow Orchestration Standard (long-running) vs Express (high-volume, short)

Security

Service What It Does Key Points IAM Access Management Policies, roles, least privilege, STS AssumeRole Cognito User Auth User Pools (tokens) vs Identity Pools (AWS credentials) KMS Key Management Envelope encryption, 4 KB limit, key rotation, cross-account Secrets Manager Secret Storage Auto-rotation, $0.40/secret/month SSM Parameter Store Config Storage Standard (free) vs Advanced, SecureString type ACM SSL/TLS Certificates Free public certs, auto-renewal, can’t export

CI/CD

Service What It Does Key Points CodeCommit Git Repository Triggers pipelines on push CodeBuild Build Service buildspec.yml, supports Docker CodeDeploy Deployment Service appspec.yml, blue/green/canary/rolling CodePipeline CI/CD Orchestration Source → Build → Test → Deploy stages SAM Serverless Framework template.yaml, sam build/deploy, local testing CloudFormation IaC Templates, stacks, change sets, !Sub, !Ref, parameters AppConfig Runtime Config Feature flags, gradual rollout, validation

Observability

Service What It Does Key Points CloudWatch Logs Log storage & Query Logs Insights query language, log groups, retention CloudWatch Metrics Metric Tracking Custom metrics, EMF, math expressions CloudWatch Alarms Alerting Metric alarms, composite alarms, SNS actions X-Ray Distributed Tracing Segments, subsegments, annotations (indexed), metadata (not indexed) CloudTrail API Audit Log Who did what? when? & Debug permission issues

2 | Numbers

Item Limit Lambda timeout 15 minutes Lambda memory 128 MB – 10,240 MB Lambda /tmp storage 512 MB – 10,240 MB Lambda deployment (zip) 50 MB compressed, 250 MB uncompressed Lambda deployment (container) 10 GB Lambda layers 5 per function, 250 MB total unzipped Lambda concurrency (default) 1,000 per region KMS direct encryption 4 KB max SQS message size 256 KB SQS visibility timeout 0s – 12 hours (default 30s) SQS retention 1 minute – 14 days (default 4 days) SNS message size 256 KB DynamoDB item size 400 KB DynamoDB GSI 20 per table DynamoDB LSI 5 per table API Gateway timeout 29 seconds API Gateway payload 10 MB S3 object size 5 TB (5 GB per PUT, use multipart for larger) Secrets Manager secret size 64 KB SSM Parameter Store (standard) 4 KB SSM Parameter Store (advanced) 8 KB *Step Functions Standard * 1 year execution Step Functions Express 5 minutes execution

3 | Patterns

Decoupling

• SQS: point-to-point, one consumer, buffering
• SNS: fanout, multiple consumers
• SNS + SQS: fanout with reliable delivery
• EventBridge: complex routing, content-based filtering

Caching

• DAX: DynamoDB reads only, microsecond latency
• ElastiCache Redis: general purpose, complex data types
• ElastiCache Memcached: simple caching, multi-threaded
• CloudFront: edge caching for APIs and static content
• API Gateway cache: per-stage, per-method caching

Authentication

• Cognito User Pool: user sign-up/sign-in, JWT tokens
• Cognito Identity Pool: temporary AWS credentials
• Lambda authorizer: custom auth logic
• IAM authorization: service-to-service with SigV4

Deployment

• AllAtOnce: fastest, highest risk
• Canary: small % first, then all (safest)
• Linear: gradual rollout over time
• Blue/Green: two environments, instant switch

Error Handling

• DLQ: capture failed messages (SQS, Lambda async)
• Lambda Destinations: route success AND failure (preferred over DLQ)
• ReportBatchItemFailures: partial batch failure for SQS
• BisectBatchOnFunctionError: split Kinesis batch to isolate bad records
• Step Functions: retry and catch at the workflow level

4 | Versus

SQS Standard vs FIFO

Feature Standard FIFO Throughput Unlimited 300 msg/s (3000 batched) Ordering Best effort Guaranteed Delivery At least once Exactly once Deduplication No Yes (5 min window)

Secrets Manager vs Parameter Store

Feature Secrets Manager Parameter Store Auto Rotation Built-in DIY Cost $0.40/secret/month Free (standard) Max Size 64 KB 4 KB / 8 KB Cross-Account Yes Yes (advanced)

Step Functions Standard vs Express

Feature Standard Express Max Duration 1 year 5 minutes Execution Model Exactly once At least once Pricing Per state transition Per execution + duration Use Case Long-running workflows High-volume, short tasks

5 | Cram

1. Lambda in VPC loses internet access → needs NAT Gateway or VPC endpoints
2. DynamoDB FilterExpression doesn’t reduce read capacity consumed
3. GSIs are eventually consistent only. No strongly consistent reads
4. DynamoDB uses Decimal, not float in Python
5. TTL deletion can take up to 48 hours after expiration
6. API Gateway timeout is 29 seconds. Can’t be increased
7. SQS FIFO throughput is 300 msg/s (3000 with batching) vs Standard (unlimited)
8. Lambda Destinations only work with async invocations
9. Provisioned concurrency costs money even when idle
10. SSE-C: you manage the key, AWS doesn’t store it. Lose the key = lose the data.
11. CloudFormation !Ref returns different things for different resources (ARN, name, ID)
12. SAM transforms to CloudFormation: sam build is required before sam deploy
13. X-Ray annotations are indexed and searchable. Metadata is not.
14. EMF is cheaper than PutMetricData for Lambda custom metrics
15. SQS long polling (WaitTimeSeconds > 0) reduces empty responses and costs

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