Design High-Performing Architectures is 24% of the SAA-C03 — about 12 of the 50 scored questions — and it has the clearest identity of the four domains: every question is a service-selection problem wearing a performance requirement. You are never asked whether a service works. You are asked which of four working services fits this workload.
Every option would run — one is right
That is the SAA signature, and this domain is where it shows most. A stem describes a workload; the four options are all genuine AWS services; each of them could be deployed without anything catching fire. What separates the correct answer is a constraint hiding in the wording: “sub-millisecond latency”, “shared file access from many instances”, “millions of requests per second”, “static IP addresses”, “not cacheable”. Train yourself to read for the constraint first and the service names second. Once you can point at the deciding phrase, the other three options stop being tempting.
The storage triangle is the most reliable discriminator
No single distinction resolves more questions in this domain than block versus file versus object — the mapping in the diagram above. Amazon EBS is block storage: a fast virtual disk attached to one EC2 instance, the home of databases and boot volumes. Amazon EFS is file storage: a shared POSIX file system that many instances mount at once, across Availability Zones, growing and shrinking on its own. Amazon S3 is object storage: objects addressed by key over HTTP at internet scale — static assets, backups, data lakes.
The access pattern in the stem picks the corner of the triangle. One instance needing a low-latency disk is EBS. Many instances needing the same files through standard file operations is EFS. Anything described as objects, assets or internet-facing content is S3. The exam will happily offer all three as options; the workload’s own words disqualify two of them.
Inside the EBS corner sits a second decision the exam loves: gp3 versus io2. gp3 is the general-purpose default and provisions up to 16,000 IOPS per volume; io2 exists for the workloads beyond that — tens of thousands of IOPS, sub-millisecond latency, higher durability. When a stem states an IOPS figure, do the arithmetic: above gp3’s ceiling, the answer is io2. The HDD types, st1 and sc1, are for cheap sequential throughput and are almost always distractors in a performance stem.
The database decision line
Databases in this domain separate along one line: what shape is the data, and how fast must a single lookup be? Tables, joins and SQL put you on the relational side — Amazon RDS, or Amazon Aurora when the stem adds demands stock engines strain under: higher throughput, more read replicas, faster failover. On the other side sits Amazon DynamoDB, and the exam signposts it with a phrase you should learn to recognise on sight: single-digit millisecond latency at any scale, usually next to “key-value” and “millions of requests”. That is DynamoDB’s own definition written into the stem. Milliseconds and relational features point left; single-digit milliseconds, key-value and extreme scale point right. Amazon Redshift appears in the options to check whether you know a data warehouse is for analytics, not operational lookups.
Read-heavy has a default answer: cache
When a stem says the same data is read over and over — a product catalog, a leaderboard, session state — and asks for the lowest possible latency, the exam’s default answer is Amazon ElastiCache. Memory beats disk by orders of magnitude, and a cache removes the repeated queries from the database rather than helping it endure them. Keep the boundary with read replicas sharp: a cache serves the same hot items at microsecond speed; replicas add capacity for varied read traffic at normal database speed. Scaling the instance vertically is the option that always lurks nearby, and it is almost never correct — it treats the symptom at full price.
The edge network has two products, not one
CloudFront and Global Accelerator both put your traffic onto AWS’s edge network, which is exactly why the exam pairs them. The split is clean: CloudFront is for cacheable HTTP content — static assets, video, APIs that benefit from caching. AWS Global Accelerator is for everything that is not cacheable: TCP and UDP flows that need static anycast IP addresses and the fastest path onto the AWS backbone. “Static IPs”, “UDP” or “not cacheable” in the stem eliminates CloudFront, no matter how global the audience sounds. And for the upload direction, remember the third edge product: S3 Transfer Acceleration, which routes long-distance uploads through the nearest edge location into a bucket using the standard S3 APIs.
The domain’s favourite wrong answer
Learn this one sentence: Multi-AZ improves availability, not performance. The classic Multi-AZ standby is a synchronous copy that serves no traffic — it exists to take over when the primary fails. Yet “enable Multi-AZ” appears in performance questions constantly, because it sounds like a second server you could put to work. When the problem is slow reads, the answer is a read replica or a cache; Multi-AZ answers a different question — what happens when an Availability Zone dies. Question 7 below is built on exactly this trap, and some version of it is waiting on the real exam.
How to use the questions below
Answer first, then read past the correct letter. In this domain the explanation of why the other three fail is the study material — each wrong option is a real service with a real job, just not this one. If you can name the phrase in the stem that eliminated it, you are practising the one skill this domain scores.
Updated for SAA-C03 (July 2026). The sample questions above are our own work
in the style of the exam — not real exam items. The exam itself is set and marked
by the certification body.