SAA-C03 Design High-Performing Architectures — 15 Questions

Question 1

A Lambda function behind API Gateway has predictable traffic spikes every hour. The function does not need access to resources in a VPC, and p95 latency spikes are caused by cold starts during scale-out. Which two actions are most effective? Select two.

Accepted Answer

Enable provisioned concurrency for the function.. Option A is correct because provisioned concurrency pre-warms a specified number of Lambda execution environments, eliminating cold starts for those instances. This directly addresses the p95 latency spikes caused by cold starts during predictable traffic spikes, as the function will have warm containers ready to handle incoming requests without the initialization delay.

Answer

Set reserved concurrency to a low fixed number.

Answer

Increase the Lambda timeout to 15 minutes.

Answer

Add an SQS dead-letter queue to reduce startup latency.

Question 2

An Aurora PostgreSQL application has an OLTP writer and a reporting dashboard that issues many read-only queries. The writer is healthy, but read latency rises noticeably during reporting windows. Which two changes should you make? Select two.

Accepted Answer

Add Aurora Replicas to scale out the read workload.. Adding Aurora Replicas (Option A) is correct because Aurora Replicas are dedicated read-only instances that share the same underlying storage volume as the writer, allowing you to scale read capacity linearly without impacting write performance. Sending read-only traffic to the reader endpoint (Option B) is correct because the reader endpoint automatically load-balances connections across all available Aurora Replicas, ensuring that dashboard queries are distributed and do not overload a single instance.

Answer

Scale up only the writer instance and keep all queries on it.

Answer

Replace the cluster with a single-AZ RDS instance to reduce replication overhead.

Answer

Move the dashboard to DynamoDB without changing the query model.

Question 3

A production application writes to an Amazon Aurora PostgreSQL cluster. Users report that during business-hour reporting runs, write latency increases. The application team wants to keep the writer focused on OLTP writes while still providing low-latency reads for reporting queries. What architectural approach should the solutions architect recommend?

Accepted Answer

Create Aurora read replicas and direct reporting read-only connections to the cluster reader endpoint.. A is correct because creating Aurora read replicas and directing reporting read-only connections to the cluster reader endpoint offloads read traffic from the writer instance. This allows the writer to focus on OLTP writes, while the reader endpoint load-balances read-only queries across replicas, providing low-latency reads for reporting without impacting write performance.

Answer

Resize the writer instance to a larger class so it can handle both writes and reads with fewer slowdowns.

Answer

Enable cross-region replication for the entire cluster so reporting always runs in the secondary Region.

Answer

Disable read replicas and use caching only in the application layer, keeping all queries connected to the writer endpoint.

Question 4

A DynamoDB table stores device status items. The partition key is deviceId, and the partition distribution is healthy (no single partition dominates). However, during peak periods the application experiences high read latency because many clients repeatedly request the latest status for the same devices. Which action best improves read latency without changing the DynamoDB partitioning model?

Accepted Answer

Add Amazon DAX as a caching layer in front of DynamoDB and route repeated read operations through DAX.. Amazon DAX is a fully managed, in-memory cache for DynamoDB that provides microsecond read latency. By caching the results of repeated GetItem and Query requests for the same device status items, DAX offloads read traffic from the underlying DynamoDB table, reducing the number of read capacity units consumed and eliminating the latency caused by repeated fetches from disk. This directly addresses the high read latency during peak periods without altering the existing partition key or partitioning model.

Answer

Change the partition key to a random value for each request to eliminate hot partitions.

Answer

Increase write capacity only, because writes generally determine read latency in DynamoDB.

Answer

Create an additional Global Secondary Index (GSI) and read exclusively from the index to accelerate reads.

Question 5

A team is splitting a new workload into two fronts. The first front serves HTTPS microservices that need host- and path-based routing plus health checks. The second front must handle TCP and UDP traffic for a real-time service and preserve static IP addresses for firewall allowlisting. Which two AWS load balancer choices best match these requirements? Select two.

Accepted Answer

Application Load Balancer. The Application Load Balancer (ALB) is correct because it supports host-based and path-based routing for HTTP/HTTPS traffic, which is essential for the microservices front. It also provides health checks at the target group level, enabling automatic routing away from unhealthy instances. ALB operates at Layer 7, making it ideal for the HTTPS microservices requirement.

Answer

Amazon API Gateway

Answer

Amazon CloudFront

Answer

Gateway Load Balancer

Question 6

An API team runs an AWS Lambda function behind an Application Load Balancer (ALB). During predictable hourly traffic spikes, p95 response latency increases due to occasional cold starts. The team wants stable latency during those spikes without permanently overprovisioning resources for all functions. Which configuration is the most appropriate way to reduce cold starts for this Lambda function?

Accepted Answer

Publish a version of the function and configure provisioned concurrency on an alias, using autoscaling for the alias.. Provisioned concurrency initializes a specified number of execution environments in advance, keeping them warm and ready to handle requests without cold start latency. By configuring provisioned concurrency on an alias with autoscaling, the team can dynamically adjust the number of pre-warmed environments to match predictable traffic spikes, avoiding permanent overprovisioning while ensuring stable p95 latency.

Answer

Increase the function memory size and rely on faster initialization to reduce cold starts.

Answer

Set reserved concurrency equal to the expected peak requests per second for the function.

Answer

Use an event source mapping with a higher batch size so Lambda triggers earlier and keeps the runtime warm.

Question 7

A distributed simulation launches 40 EC2 instances that exchange small packets frequently and are sensitive to cross-instance latency. The workload stays in one Availability Zone and can use the same instance family across nodes. Which two choices improve network performance the most? Select two.

Accepted Answer

Launch all instances in a cluster placement group.. A cluster placement group provides low-latency, high-bandwidth network connectivity by placing instances in a single Availability Zone within the same logical rack or cluster. This minimizes cross-instance latency and maximizes throughput for frequent small-packet exchanges, which is ideal for tightly coupled distributed simulations.

Answer

Place the instances across several Availability Zones for higher aggregate resilience.

Answer

Use a spread placement group to pack the instances tightly together.

Answer

Put the workload behind CloudFront so internal node communication is faster.

Question 8

A Lambda function behind an API needs consistent low latency. Traffic normally drops to near zero, then spikes several times per hour. During spikes, the p95 latency often spikes above 800 ms due to cold starts. The team wants to keep using Lambda (no containers) but minimize cold start impact during predictable spikes. What is the best AWS configuration to meet this goal?

Accepted Answer

Enable Lambda provisioned concurrency on a published function alias and set the minimum provisioned instances to the baseline expected during spikes.. Provisioned concurrency initializes a specified number of execution environments in advance, keeping them warm and ready to handle requests instantly. By setting the minimum provisioned instances to the baseline expected during spikes, the function avoids cold starts for those requests, ensuring p95 latency stays low even when traffic surges from near zero.

Answer

Increase the function memory size to the maximum and rely on the larger memory to eliminate cold starts.

Answer

Configure an ALB with target group health checks to keep Lambda warm by sending periodic requests.

Answer

Turn on AWS CloudTrail data events to monitor cold start frequency and tune the runtime accordingly.

Question 9

A media processing service runs ECS tasks in multiple Availability Zones. Each task must read and write the same shared filesystem with low latency because tasks stream intermediate artifacts to other tasks. The team currently mounts an EBS volume per task, and cross-AZ tasks frequently cannot see each other’s files. Which option best resolves the shared filesystem requirement while supporting high-performing access?

Accepted Answer

Use Amazon EFS with mount targets in each Availability Zone so all tasks mount a common NFS filesystem over the AWS network.. Amazon EFS provides a fully managed, shared NFS filesystem that can be mounted concurrently by ECS tasks across multiple Availability Zones with low latency. It supports POSIX file operations, making it ideal for streaming intermediate artifacts between tasks. EFS mount targets in each AZ ensure local access, meeting the requirement for high-performing shared storage.

Answer

Keep using EBS, but attach the same EBS volume to tasks in multiple Availability Zones using EBS multi-attach so all tasks share the filesystem.

Answer

Use Amazon S3 for the intermediate artifacts and rely on S3 event notifications to emulate POSIX file operations.

Answer

Switch to instance store on each task and use SQS messages between tasks to copy intermediate artifacts.

Question 10

An application uses DynamoDB to store order status. Reads happen extremely frequently for the same few keys (for example, the most recent orders), and the team wants lower read latency without changing the table’s partition key design. Which AWS service best fits this requirement?

Accepted Answer

Amazon DAX (DynamoDB Accelerator) to cache frequently read items. Amazon DAX (DynamoDB Accelerator) is an in-memory cache that sits between your application and DynamoDB, providing microsecond read latency for frequently accessed items. Because the workload involves extremely frequent reads of the same few keys (hot keys), DAX reduces the load on the DynamoDB table and delivers faster responses without requiring any changes to the partition key design.

Answer

Provision AWS WAF rules to reduce DynamoDB read latency caused by bots

Answer

Enable multi-region writes in DynamoDB Global Tables to speed up reads locally

Answer

Add more read capacity units to DynamoDB and avoid caching entirely

Question 11

A company serves the same public content to many users through Amazon CloudFront. The origin is experiencing increased fetches because CloudFront cache hit rate is dropping. Most requests include an Authorization header and a custom header that changes per user. The response content is identical regardless of these headers. What change should the solutions architect make to restore a high cache hit rate?

Accepted Answer

Create a custom cache policy that excludes the Authorization header and the per-user changing custom header from the cache key.. Option A is correct because CloudFront's default cache key includes the Authorization header and all custom headers, which causes unique cache entries for each user even though the content is identical. By creating a custom cache policy that excludes these headers from the cache key, CloudFront will treat requests with different header values as the same cached object, restoring a high cache hit rate and reducing origin fetches.

Answer

Lower the TTL to a few seconds so cached objects expire sooner and origin fetches decrease.

Answer

Disable caching for the affected paths so CloudFront always forwards all headers to the origin.

Answer

Force all requests to use query-string based caching and include all headers in the cache policy for correctness.

Question 12

Your team runs a tightly coupled distributed workload (for example, synchronous training nodes) across many EC2 instances placed within a single cluster environment. The instances need low-latency networking to reduce delays at synchronization barriers. Which EC2 placement strategy should you use to improve inter-node latency?

Accepted Answer

Create a placement group with the 'cluster' strategy to place instances close together and reduce network latency.. A cluster placement group is the correct choice because it groups instances in a single Availability Zone with low-latency, high-bandwidth networking, ideal for tightly coupled workloads like synchronous training nodes that require minimal delay at synchronization barriers. This strategy places instances physically close together within the same rack or cluster, reducing network round-trip time and maximizing throughput for inter-node communication.

Answer

Create a placement group with the 'spread' strategy to separate instances across underlying hardware for fault tolerance.

Answer

Use the default placement strategy and rely on Auto Scaling to keep instances from drifting to different locations.

Answer

Avoid placement groups and instead use Amazon S3 for inter-node messaging to minimize direct network traffic between instances.

Question 13

An order lookup API repeatedly reads the same few items from DynamoDB. The application can tolerate slightly stale data for a few seconds, and the team wants the lowest-latency design with minimal application changes. Which two changes should they make? Select two.

Accepted Answer

Put Amazon DynamoDB Accelerator (DAX) in front of the table.. Amazon DynamoDB Accelerator (DAX) is an in-memory cache for DynamoDB that provides microsecond read latency, which is ideal for repeated reads of the same few items. Since the application can tolerate slightly stale data, DAX's default write-through caching with a TTL of 5 minutes ensures low latency without requiring application code changes beyond adding the DAX client.

Answer

Switch all access to strongly consistent reads for faster results.

Answer

Increase the item size so fewer requests are needed.

Answer

Replace the table with Amazon EBS volumes mounted on EC2 instances.

Question 14

A team needs to distribute TCP traffic (not HTTP) across multiple services. The services must see the original client source IP for auditing. Which AWS load balancer is the best fit?

Accepted Answer

Network Load Balancer (NLB) using TCP listeners. A Network Load Balancer (NLB) is the best fit because it operates at Layer 4 (TCP/UDP) and preserves the original client source IP address by default, which is required for auditing. It can distribute raw TCP traffic across multiple services without inspecting application-layer headers, making it ideal for non-HTTP TCP workloads.

Answer

Application Load Balancer (ALB) using HTTP/HTTPS listeners with host-based routing

Answer

Classic Load Balancer (CLB) configured for TCP health checks only

Answer

API Gateway with a VPC Link to forward raw TCP traffic

Question 15

Your team hosts versioned static assets (for example, /static/app-<buildHash>.js). Each build hash never changes, but you release new files on new URLs. To maximize cache hit rate and reduce origin load using CloudFront, what should you do when generating HTTP responses for these assets?

Accepted Answer

Set Cache-Control: public, max-age=31536000, immutable for the versioned assets. Option B is correct because setting `Cache-Control: public, max-age=31536000, immutable` tells CloudFront and browsers to cache the versioned asset for one year (31536000 seconds) and never revalidate, since the URL changes with each new build. The `immutable` directive (RFC 8246) signals that the content will never change on that URL, eliminating conditional revalidation requests and maximizing cache hits, which reduces origin load.

Answer

Set Cache-Control: no-cache so CloudFront always revalidates with the origin

Answer

Set Cache-Control: max-age=0 and rely on CloudFront to cache by default

Answer

Disable CloudFront caching and forward all headers and query strings to the origin