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

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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

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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

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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

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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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