SAA-C03 Design High-Performing Architectures Practice Test 14 — 15 Questions

Question 1

A media platform runs a CPU-heavy thumbnail generation workload on an EC2 Auto Scaling group using t3.large instances. During peak traffic, p95 processing time increases significantly even though average CPU remains around 40–50%. CloudWatch also shows CPU credit depletion behavior. Which change will most directly improve performance predictability for this workload?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Change the Auto Scaling group instance type to a compute-optimized family (for example, c7i) to provide steady CPU performance.. The t3.large instances rely on CPU credits for burst performance, and when credits are exhausted, CPU performance is throttled to the baseline (e.g., 30% for t3.large). This causes unpredictable processing times during peak traffic, even if average CPU is moderate. Switching to a compute-optimized family like c7i provides dedicated, consistent CPU performance without credit-based throttling, directly improving predictability for CPU-heavy thumbnail generation.

Answer

Increase the t3.large maximum CPU credits and keep the Auto Scaling group using the same burstable instance type.

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Add a placement group to the existing t3.large instances so they are packed close together for lower latency between nodes.

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Switch the workload to run on Lambda with the same logic so invocations automatically scale without instance selection changes.

Question 2

Your company needs a high-throughput, low-latency TCP service using a custom binary protocol. Requirements: preserve the original client source IP for rate limiting, keep latency minimal, and use TCP health checks. The current setup uses an Application Load Balancer and performance is inconsistent. Which load balancer choice best meets these requirements?

Accepted Answer

Use a Network Load Balancer (NLB) with TCP listeners so traffic stays at Layer 4 and the original source IP is preserved.. A Network Load Balancer (NLB) operates at Layer 4 and preserves the original client source IP by default, which is essential for accurate rate limiting. Its TCP listeners provide low-latency, high-throughput handling of custom binary protocols, and it supports TCP health checks natively. This directly addresses the performance inconsistency seen with the Application Load Balancer, which operates at Layer 7 and introduces additional processing overhead.

Answer

Keep the Application Load Balancer (ALB), because ALBs also preserve client source IP for TCP protocols.

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Use Amazon API Gateway because it preserves client source IP and provides TCP health checks for all protocols.

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Use Amazon CloudFront with an S3 origin, because CloudFront reduces latency for TCP-based protocols.

Question 3

A site serves static assets (JS/CSS) through CloudFront from an S3 origin. After a recent frontend change, CloudFront shows a cache hit ratio below 20%. In CloudFront access logs, requests to the same asset URL path differ by a query parameter named rnd (a random value appended by the app on every request). The origin content is identical regardless of rnd. What is the best CloudFront configuration change to restore effective caching?

Accepted Answer

Create a custom CloudFront Cache Policy that does not include the rnd query parameter in the cache key (whitelist only required parameters, or forward no query strings).. The rnd query parameter makes each request appear unique to CloudFront, causing a cache miss for every request even though the underlying content is identical. By creating a custom cache policy that either forwards no query strings or whitelists only required parameters, CloudFront will ignore the rnd parameter when computing the cache key, allowing it to serve cached responses and dramatically improve the cache hit ratio.

Answer

Increase the origin response Cache-Control max-age header on S3 so CloudFront caches longer even with different rnd values.

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Disable compression on CloudFront so the response body is identical byte-for-byte and cache hits improve.

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Switch the origin from S3 to an ALB so CloudFront can cache based on ALB target health checks instead of the query string.

Question 4

An event ingestion service writes to a DynamoDB table where the partition key is tenantId and the sort key is eventTime. During a campaign, one tenant generates a disproportionate share of traffic, causing write throttling and increased latency for that tenant’s writes. You can change the data model and application queries, but you must still efficiently retrieve events for a tenant for the last 10 minutes. Which change best improves write throughput by reducing hot partitions?

Accepted Answer

Add a shard attribute to the partition key (partition key = tenantId#shard, where shard is randomly selected from a fixed range). Query all shards for the tenant for eventTime values in the last 10 minutes, then merge results in the application.. It distributes writes for a hot tenant across multiple partitions by appending a random shard suffix to the tenantId partition key. This eliminates a single hot partition, allowing DynamoDB to scale write capacity horizontally. The application can then query all shards for the last 10 minutes and merge results, satisfying the retrieval requirement.

Answer

Keep tenantId as the partition key and rely on DynamoDB adaptive capacity to automatically remove all throttling.

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Change the sort key to eventTimeBucket (for example, eventTime rounded to 1-minute buckets) while keeping the partition key as tenantId.

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Enable DAX and use it for write operations so throttled writes are served from cache instead of reaching DynamoDB.

Question 5

A serverless checkout API runs on AWS Lambda behind API Gateway. Traffic spikes are predictable every weekday at 09:00 UTC, and p95 latency jumps for the first few minutes after each deployment because execution environments are cold. The team wants to reduce this startup impact without changing the API contract. Which changes should they make? Select three.

Accepted Answer

Configure provisioned concurrency on the production Lambda alias during the busy windows.. Provisioned concurrency initializes a specified number of execution environments in advance, so when traffic spikes at 09:00 UTC, the Lambda function is already warm and can serve requests without cold start latency. This directly addresses the p95 latency jump after deployment without altering the API contract.

Answer

Replace provisioned concurrency with reserved concurrency because reserved concurrency keeps instances warm.

Answer

Increase the function timeout so the first request has more time to warm up.

Question 6

A company serves public JavaScript and CSS files from S3 using CloudFront. After a frontend change, customers report a low CloudFront cache hit ratio. Requests now include an Authorization header, but these assets do not require authentication. The CloudFront distribution is configured such that Authorization is included in the cache key. Which change best maximizes cache reuse?

Accepted Answer

Use a CloudFront Cache Policy that excludes Authorization from the cache key. Excluding the Authorization header from the cache key ensures that all users, regardless of their authentication token, receive the same cached object. Since the static assets (JavaScript/CSS) do not require authentication, including Authorization in the cache key creates multiple cache entries for the same file, drastically reducing the cache hit ratio. A CloudFront cache policy that omits Authorization from the cache key maximizes reuse while still allowing the header to be forwarded to the origin if needed.

Answer

Include the Authorization header in the cache key so responses vary correctly

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Disable caching and always fetch from S3

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Forward all headers and cookies to the origin to improve correctness

Question 7

Based on the exhibit, an application runs on Amazon Aurora MySQL. The writer instance is frequently near 85% CPU while the reader instance is under 20% CPU. Application traces show that most of the database traffic is read-only SELECT queries, but the code currently sends all queries to the writer endpoint. What should the solutions architect recommend to improve performance with the smallest functional change?

Accepted Answer

Point read-only database traffic to the Aurora reader endpoint and keep writes on the writer endpoint.. The Aurora reader endpoint distributes read-only traffic across all available reader instances, offloading the writer instance and reducing its CPU utilization. Since the application traces show most traffic is read-only SELECT queries, this change requires only modifying the connection string for reads while keeping writes on the writer endpoint, making it the smallest functional change.

Answer

Increase the writer instance size and keep all traffic on the writer endpoint.

Answer

Convert the cluster to a Multi-AZ RDS PostgreSQL deployment to get automatic failover and better read performance.

Answer

Enable cross-Region read replicas so SELECT queries are routed to a remote Region for improved performance.

Question 8

Based on the exhibit, a static asset distribution site uses Amazon CloudFront with an S3 origin. The assets are versioned by filename, but the cache hit ratio remains low after each release. Which CloudFront change is the best way to improve cache reuse without changing the origin objects?

Accepted Answer

Remove Authorization and unnecessary query strings from the CloudFront cache key.. Removing Authorization headers and unnecessary query strings from the CloudFront cache key ensures that multiple requests for the same versioned asset (e.g., style.v2.css) share a single cached object, regardless of user-specific headers or irrelevant query parameters. This directly increases the cache hit ratio without modifying the origin objects, as CloudFront will serve the same cached response for identical cache keys.

Answer

Keep the current cache key and increase the S3 bucket's storage class.

Answer

Disable the CloudFront cache so every request is served directly from S3.

Answer

Switch the origin from Amazon S3 to an Application Load Balancer.

Question 9

Based on the exhibit, a single EC2 instance hosts a latency-sensitive cache that performs sustained random reads and writes to persistent block storage. The current EBS volume is a general-purpose SSD, but BurstBalance is repeatedly depleted and p95 I/O latency has risen above 20 ms. The workload needs more than 16,000 sustained IOPS. Which change is the best fix?

Accepted Answer

Replace the volume with an io2 EBS volume and provision the required IOPS.. The workload requires more than 16,000 sustained IOPS with low latency, and the gp2 volume's burst credits are exhausted, causing high latency. An io2 Block Express or io2 volume can be provisioned with the exact IOPS needed (up to 256,000 IOPS) and provides consistent single-digit millisecond latency, making it the best fix for this latency-sensitive, sustained I/O workload.

Answer

Move the data to Amazon S3 so the instance can read and write objects directly.

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Keep gp2 and increase the instance size to a compute-optimized family.

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Enable Amazon EFS with bursting throughput mode for the cache data.

Question 10

A media company serves versioned JavaScript and CSS files from Amazon S3 through CloudFront. After each release, the cache hit ratio drops sharply because the same distribution also fronts a personalized API path, and the current cache policy forwards cookies, all query strings, and several headers to every origin request. The static assets already use content-hashed filenames. Which two changes will most directly improve cache hit ratio for the static assets without changing the application behavior? Select two.

Accepted Answer

Create a dedicated cache behavior for the static asset path that excludes cookies, query strings, and unneeded headers from the cache key.. Creating a dedicated cache behavior for the static asset path (e.g., /static/*) allows you to configure a cache policy that excludes cookies, query strings, and unneeded headers from the cache key. Since the static assets use content-hashed filenames, they are immutable and do not vary by user-specific attributes. By removing these variables from the cache key, CloudFront can serve the same cached object to all users, drastically improving the cache hit ratio.

Answer

Increase the size of the S3 bucket’s underlying storage to absorb more origin traffic.

Answer

Add Lambda@Edge logic to append a timestamp to every asset request so updates are always fetched immediately.

Answer

Disable compression so CloudFront can treat each object as a separate cache entry.

Question 11

A retail analytics table stores events in Amazon DynamoDB with partition key tenantId and sort key eventTime. During a promotion, one tenant generates most writes and repeatedly polls the same latest-status items, causing throttling on a single partition key and high latency on reads. The business can tolerate read results that are a few seconds stale. Which two changes will most effectively reduce throttling and latency? Select two.

Accepted Answer

Introduce write sharding by adding a bounded random suffix to the hot tenant partition key and fan out reads across the shards.. Write sharding distributes the hot tenant's writes across multiple partitions by appending a bounded random suffix to the partition key, preventing a single partition from throttling. Reads then fan out across all shards and aggregate results, which is acceptable since the business tolerates a few seconds of staleness. This directly addresses the single-partition bottleneck without changing the overall data model.

Answer

Keep the same key design and increase only the table’s provisioned RCUs and WCUs.

Answer

Replace the table reads with a Scan operation to distribute the load across all partitions.

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Move the table to another Availability Zone so the hot tenant uses a different storage node.

Question 12

A distributed analytics engine runs 12 EC2 instances in one Availability Zone. The nodes exchange thousands of tiny messages per second and must keep jitter as low as possible. The current design launches the instances across multiple placement groups and uses general-purpose burstable instances. Which two changes will most directly lower east-west network latency and variability? Select two.

Accepted Answer

Move all instances into a cluster placement group.. A cluster placement group provides a low-latency, high-bandwidth network connection by placing instances in a single Availability Zone within the same logical rack or cluster. This minimizes the physical distance and network hops between instances, directly reducing east-west latency and jitter for the thousands of tiny messages per second.

Answer

Spread the instances across three Availability Zones for better fault tolerance.

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Front the nodes with an Application Load Balancer to balance the internal messages.

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Store the messages on EBS volumes so the nodes avoid network communication.

Question 13

A serverless checkout API uses AWS Lambda behind API Gateway. Every weekday at 09:00 UTC, marketing triggers a predictable surge. The first few minutes after each surge show cold-start latency, but traffic volume is forecastable and the business wants stable p95 latency. Which two changes should the team implement? Select two.

Accepted Answer

Publish a Lambda version and attach provisioned concurrency to an alias that points to that version.. Provisioned concurrency keeps a specified number of Lambda execution environments initialized and ready to respond immediately, eliminating cold starts for predictable traffic patterns. By publishing a Lambda version and attaching provisioned concurrency to an alias pointing to that version, the team ensures that the surge at 09:00 UTC is handled without cold-start latency, stabilizing p95 latency.

Answer

Increase the Lambda timeout so the function has more time to initialize during the spike.

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Double the memory size during the spike without changing the concurrency model.

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Move the function into more Availability Zones so the platform can spread cold starts across regions.

Question 14

A partner integration sends a custom binary TCP protocol to a service running on EC2 instances in private subnets. The partners require static endpoint IPs for allowlisting, and the application must see the original client source IP for rate limiting. Which two changes best fit the protocol and network requirements? Select two.

Accepted Answer

Replace the Application Load Balancer with a Network Load Balancer.. A Network Load Balancer (NLB) is required because it supports TCP traffic natively at Layer 4, which is necessary for a custom binary TCP protocol that cannot be interpreted by an Application Load Balancer (ALB) at Layer 7. Additionally, an NLB preserves the original client source IP address by default when used with targets in private subnets, meeting the requirement for rate limiting based on the client IP. Static IP addresses can be assigned to the NLB via Elastic IPs, satisfying the partner's need for static endpoint IPs for allowlisting.

Answer

Put the service behind API Gateway REST API and use Lambda integration.

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Use CloudFront to cache the binary packets at edge locations.

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Terminate the traffic with an Amazon RDS proxy to stabilize the connections.

Question 15

An application uses Amazon Aurora MySQL. CloudWatch shows the writer instance near 85% CPU while the only reader instance averages 15% CPU. Trace logs show that all SELECT statements still target the writer endpoint. The workload is read-heavy, and the application already tolerates eventual consistency for reads. Which two changes will best increase total read throughput without a schema redesign? Select two.

Accepted Answer

Point read-only queries to the Aurora reader endpoint instead of the writer endpoint.. The Aurora reader endpoint is designed to distribute read-only connections across all available Aurora Replicas, offloading SELECT queries from the writer instance. Currently, all SELECT statements target the writer endpoint, causing the writer's CPU to be at 85% while the reader instance is underutilized at 15%. By redirecting read traffic to the reader endpoint, the writer's CPU load decreases, and the existing reader instance can handle more read throughput without any schema changes.

Answer

Convert the cluster to a single-AZ RDS MySQL instance to reduce replication overhead.

Answer

Replace the writer endpoint with the instance endpoint of the primary node to speed up SELECT queries.

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Add Amazon ElastiCache and move all database writes into the cache layer.