Multi-Service Tradeoff — AWS SysOps Administrator (SOA-C03)
Operational Ownership Separates Container from Serverless
Requirement: process variable-volume events with custom business logic. Competing choices: ECS task, EKS pod, Lambda function, SQS-triggered worker. The deciding constraint is operational ownership scope. ECS and EKS both run containers but retain cluster infrastructure responsibility. Lambda removes it entirely within execution time limits. SQS decouples the producer but still needs a compute consumer. The exam expects you to trace which option removes the most undifferentiated burden for the scenario's workload profile.
What This Pattern Tests
The exam gives you a decoupling requirement and tests whether you pick the right messaging service. SQS is point-to-point with at-least-once delivery (Standard) or exactly-once (FIFO, 3,000 msg/s with batching). SNS is pub/sub fan-out to multiple subscribers. EventBridge is content-based routing with schema registry and 35+ AWS service sources. The trap is choosing SQS for fan-out (use SNS) or SNS for ordered processing (use SQS FIFO). DynamoDB vs. Aurora vs. ElastiCache follows the same pattern: key-value at any scale vs. relational joins vs. microsecond reads from memory.
Decision Axis
Communication pattern (point-to-point vs. fan-out vs. content routing) and data access pattern (key-value vs. relational vs. cache) determine the service.
Associated Traps
Decision Rules
Scope EBS Fast Snapshot Restore to only the single most recent recovery snapshot in the primary Availability Zone rather than enabling it broadly across all retained snapshots and multiple AZs, to satisfy the 30-minute RTO without breaching the cost ceiling.
Whether transitioning EBS snapshots to cold storage satisfies a 30-minute RTO, or whether multi-hour archive retrieval latency forces standard-tier retention with cost controlled through deletion lifecycle policies rather than storage-tier degradation.
Select the S3 storage class whose retrieval SLA fits within 30 minutes at the lowest available per-GB price, recognising that S3 Glacier Instant Retrieval provides millisecond access at a fraction of S3 Standard cost while S3 Glacier Flexible Retrieval Standard (3–5 hours) fails the RTO even though its storage price is marginally lower.
Select AWS Service Catalog over AWS CDK when the operator team has no programming expertise and centralized governance enforcement with a self-service interface is an explicit requirement.
When operator skill is limited and governance enforcement is mandatory, Service Catalog (wrapping a CloudFormation template) wins over CDK or raw CloudFormation because it separates template authorship from deployment, enforces tag constraints centrally, and exposes a no-code self-service interface.
Domain Coverage
Difficulty Breakdown