Lambda Provisioned Concurrency: Eliminate Cold Starts During Predictable Traffic Spikes
This SAA-C03 practice question tests your understanding of design high-performing architectures. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Lambda logs:
REPORT RequestId: 9d6b... Duration: 184.27 ms Billed Duration: 185 ms Memory Size: 1024 MB Max Memory Used: 612 MB Init Duration: 812.43 ms
Traffic pattern:
- Low traffic outside weekdays 09:00-09:15 UTC
- Predictable spike every weekday
- Function language: Python 3.12
- No need to keep spare capacity all day
Based on the exhibit, a serverless checkout API is implemented in AWS Lambda and deployed in one Region. The function has a cold-start time of 700-900 ms on the first request after idle periods. Marketing launches a predictable traffic spike every weekday at 09:00 UTC, and the p95 latency target is under 150 ms during the first five minutes of the spike. What should the solutions architect do to meet the latency target while controlling cost?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Exhibit
Lambda logs:
REPORT RequestId: 9d6b... Duration: 184.27 ms Billed Duration: 185 ms Memory Size: 1024 MB Max Memory Used: 612 MB Init Duration: 812.43 ms
Traffic pattern:
- Low traffic outside weekdays 09:00-09:15 UTC
- Predictable spike every weekday
- Function language: Python 3.12
- No need to keep spare capacity all day
A
Increase the Lambda memory size and leave concurrency at the default value.
Why wrong: More memory can improve execution speed, but it does not eliminate cold starts when a function has been idle.
B
Configure provisioned concurrency and scale it up before the predictable spike begins.
Provisioned concurrency keeps pre-initialized environments ready, which removes most cold-start latency. Because the spike is predictable, you can scale concurrency before 09:00 UTC and reduce it afterward to control cost.
C
Put the Lambda function behind an Application Load Balancer so the load balancer absorbs the initialization delay.
Why wrong: An ALB does not remove Lambda initialization time; it only changes how requests are routed to the function.
D
Set reserved concurrency to the expected peak so Lambda will pre-create execution environments.
Why wrong: Reserved concurrency limits concurrent executions, but it does not pre-warm execution environments or eliminate cold starts.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure provisioned concurrency and scale it up before the predictable spike begins.
Provisioned concurrency pre-warms a specified number of execution environments so that the Lambda function has zero cold-start latency when invoked. By scheduling the provisioned concurrency to scale up before the 09:00 UTC spike, the function can serve the first requests within the 150 ms p95 latency target, while the scheduled scaling down after the spike controls cost by releasing unused capacity.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Increase the Lambda memory size and leave concurrency at the default value.
Why it's wrong here
More memory can improve execution speed, but it does not eliminate cold starts when a function has been idle.
✓
Configure provisioned concurrency and scale it up before the predictable spike begins.
Why this is correct
Provisioned concurrency keeps pre-initialized environments ready, which removes most cold-start latency. Because the spike is predictable, you can scale concurrency before 09:00 UTC and reduce it afterward to control cost.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Put the Lambda function behind an Application Load Balancer so the load balancer absorbs the initialization delay.
Why it's wrong here
An ALB does not remove Lambda initialization time; it only changes how requests are routed to the function.
✗
Set reserved concurrency to the expected peak so Lambda will pre-create execution environments.
Why it's wrong here
Reserved concurrency limits concurrent executions, but it does not pre-warm execution environments or eliminate cold starts.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the distinction between provisioned concurrency (which pre-warms environments to eliminate cold starts) and reserved concurrency (which only caps the maximum concurrent executions without affecting cold-start behavior).
Detailed technical explanation
How to think about this question
Provisioned concurrency works by keeping a specified number of execution environments initialized and ready to handle requests, effectively eliminating the cold-start latency for those environments. Under the hood, AWS Lambda pre-warms the runtime and initializes the function code, so the first invocation after idle periods experiences no delay. In real-world scenarios, this is critical for applications with predictable traffic spikes, such as e-commerce flash sales or daily batch processing, where even a 700 ms cold start would cause unacceptable latency.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
Quick reference
Cloud Service Model Comparison
Model
You Manage
Provider Manages
Examples
IaaS
OS, runtime, apps, data
Hardware, hypervisor, networking
EC2, Azure VMs, GCP Compute Engine
PaaS
Apps and data
OS, runtime, middleware, hardware
Elastic Beanstalk, Azure App Service
SaaS
Data and settings only
Everything else
Microsoft 365, Salesforce, Workday
FaaS / Serverless
Function code only
Infra, scaling, runtime
Lambda, Azure Functions, Cloud Run
CaaS
Containers and apps
Kubernetes, OS, hardware
EKS, AKS, GKE
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design High-Performing Architectures — This question tests Design High-Performing Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure provisioned concurrency and scale it up before the predictable spike begins. — Provisioned concurrency pre-warms a specified number of execution environments so that the Lambda function has zero cold-start latency when invoked. By scheduling the provisioned concurrency to scale up before the 09:00 UTC spike, the function can serve the first requests within the 150 ms p95 latency target, while the scheduled scaling down after the spike controls cost by releasing unused capacity.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A Lambda-based travel booking site has unpredictable traffic spikes and users see latency caused by cold starts. The function must respond consistently during expected campaign windows. What should be configured?
hard
✓ A.Provisioned concurrency during campaign windows
B.A larger deployment package
C.CloudTrail data events
D.Reserved concurrency only
Why A: Provisioned concurrency initializes a specified number of execution environments in advance, eliminating cold starts for those instances. During campaign windows, this ensures consistent sub‑millisecond latency because the function is always warm and ready to handle requests immediately.
Variation 2. A Lambda-based travel booking site has unpredictable traffic spikes and users see latency caused by cold starts. The function must respond consistently during expected campaign windows. What should be configured? The team wants the control to be enforceable during normal operations.
hard
✓ A.Provisioned concurrency during campaign windows
B.A larger deployment package
C.CloudTrail data events
D.Reserved concurrency only
Why A: Provisioned concurrency initializes a specified number of execution environments in advance, eliminating cold starts for those instances. During campaign windows, this ensures consistent latency by keeping functions warm and ready to handle spikes immediately. The team can enforce this configuration only during expected high-traffic periods, leaving normal operations unaffected.
Variation 3. A Lambda-based travel booking site has unpredictable traffic spikes and users see latency caused by cold starts. The function must respond consistently during expected campaign windows. What should be configured? The design must avoid adding custom operational scripts.
hard
✓ A.Provisioned concurrency during campaign windows
B.A larger deployment package
C.CloudTrail data events
D.Reserved concurrency only
Why A: Provisioned concurrency keeps a specified number of Lambda execution environments initialized and ready to respond immediately, eliminating cold starts. By enabling it only during campaign windows, you ensure consistent latency for the travel booking site during traffic spikes without incurring cost during off-peak periods. This directly addresses the requirement to avoid custom scripts, as it is a native AWS feature configured via the Lambda API or console.
Variation 4. Based on the exhibit, a serverless API on AWS Lambda experiences a predictable cold-start penalty every weekday at 09:00 UTC when a marketing campaign begins. The team wants the first requests to stay fast while minimizing extra cost during quiet periods. What is the best approach?
hard
✓ A.Enable provisioned concurrency on the published version and schedule it to scale up shortly before the spike.
B.Increase the Lambda timeout so cold starts have more time to complete.
C.Move the function behind an Application Load Balancer to improve warm-up behavior.
D.Increase the function memory to the maximum value and leave concurrency unchanged.
Why A: Provisioned concurrency pre-warms a specified number of Lambda execution environments so that incoming requests do not incur a cold start. By scheduling the provisioned concurrency to scale up just before the 09:00 UTC spike and scale down afterward, the team eliminates the cold-start penalty during the campaign while minimizing cost during quiet periods. This directly addresses the predictable, time-bound traffic pattern without requiring code changes or over-provisioning.
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