DVA-C02 Development with AWS Services Practice Question
A developer has written an AWS Lambda function that processes messages from an Amazon SQS queue. The function is configured with a reserved concurrency of 5. The SQS queue has 10,000 messages waiting to be processed. What will happen when the Lambda function is invoked?
⚠ Common exam trap
A common mix-up: candidates assume Lambda will automatically scale to handle the queue depth, but reserved concurrency is a hard limit that prevents scaling beyond the configured value, leading to throttling rather than rejection or automatic scaling.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Lambda will process messages with a maximum of 5 concurrent executions, each processing a batch of messages.
AWS Lambda integrates with Amazon SQS to poll the queue and invoke the function with batches of messages. The reserved concurrency of 5 caps the maximum number of concurrent executions, so Lambda will process messages with up to 5 concurrent invocations, each receiving a batch of up to 10 messages (default batch size). The remaining messages remain in the queue until they are processed or the visibility timeout expires.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Lambda will automatically increase reserved concurrency to handle the load.
Why it's wrong here
Reserved concurrency is a static configuration set by the developer for a specific Lambda function, defining the maximum number of concurrent executions allowed. It acts as a hard upper limit and is not dynamically adjusted by AWS Lambda in response to increased invocation load. Therefore, Lambda will not automatically increase this pre-configured value to handle a surge in messages.
- ✗
Lambda will reject the invocation because reserved concurrency is too low.
Why it's wrong here
Lambda will not reject all invocations outright simply because the reserved concurrency is set to a low value. Instead, once the function reaches its reserved concurrency limit of 5, any new incoming invocations beyond that threshold will be throttled. For event sources like SQS, these throttled messages are typically returned to the queue for a later retry, not permanently rejected.
- ✗
Lambda will scale up to 20 concurrent executions to process all messages quickly.
Why it's wrong here
The primary purpose of setting reserved concurrency is to explicitly cap the maximum number of concurrent executions for a Lambda function, overriding the default account-level concurrency limits or the function's provisioned concurrency. Even if the incoming message volume is high enough to warrant 20 concurrent executions, the reserved concurrency of 5 will strictly prevent the function from scaling beyond that specified limit.
- ✓
Lambda will process messages with a maximum of 5 concurrent executions, each processing a batch of messages.
Why this is correct
This statement accurately describes the behavior of a Lambda function configured with reserved concurrency. The function will scale up to, but not exceed, the specified limit of 5 concurrent executions. Each of these concurrent executions will then process a batch of messages from the event source, ensuring that the processing adheres strictly to the defined concurrency constraint.
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 |
Go deeper
Related to this question
About these practice questions
One of 724 original DVA-C02 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.