Lambda concurrency and throttling in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the reserved concurrency limit for an AWS Lambda function.

AWS

aws lambda put-function-concurrency --function-name MyFunction --reserved-concurrent-executions [1]

Drag options to blanks, or click blank then click option'

Aunlimited

B-1

C0

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'unlimited' which is not accepted as a number.

Setting reserved concurrency to 0 disables the function.

The reserved concurrency must be a positive integer to limit concurrent executions. '10' sets the limit to 10 concurrent executions.

2fill in blank

medium

Complete the code to check the current concurrency limit of a Lambda function.

AWS

aws lambda get-function-concurrency --function-name [1]

Drag options to blanks, or click blank then click option'

AYourFunction

BLambdaFunc

CMyFunction

DFunction1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong or misspelled function name.

Confusing function name with ARN.

The command requires the exact function name. 'MyFunction' matches the example function used.

3fill in blank

hard

Fix the error in the command to remove the reserved concurrency limit from a Lambda function.

AWS

aws lambda [1] --function-name MyFunction

Drag options to blanks, or click blank then click option'

Anull

Bdelete-function-concurrency

C0

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'put-function-concurrency --reserved-concurrent-executions 0' which disables the function.

Using 'null' or 'None' which cause errors.

Use 'delete-function-concurrency' to remove the reserved concurrency configuration, allowing the function to use the full account concurrency limit.

4fill in blank

hard

Fill both blanks to set the reserved concurrency limit to 1000 for a Lambda function (causing throttling beyond 1000 concurrent invocations).

AWS

aws lambda put-function-concurrency --function-name MyFunction --[2] [1]

Drag options to blanks, or click blank then click option'

A1000

Bthrottle

Creserved-concurrent-executions

Dconcurrency-limit

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid parameter names like 'throttle' or 'concurrency-limit'.

Confusing with provisioned concurrency parameters.

The command sets --reserved-concurrent-executions 1000 to limit the function to 1000 concurrent executions.

5fill in blank

hard

Fill all three blanks to create a CloudWatch alarm that triggers when Lambda throttling exceeds 5 errors in 1 minute.

AWS

aws cloudwatch put-metric-alarm --alarm-name LambdaThrottleAlarm --metric-name Throttles --namespace AWS/Lambda --statistic [1] --period [2] --threshold [3] --comparison-operator GreaterThanThreshold --evaluation-periods 1 --alarm-actions arn:aws:sns:us-east-1:123456789012:NotifyMe

Drag options to blanks, or click blank then click option'

ASum

BAverage

C60

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Average' instead of 'Sum' which may not catch total throttles.

Setting threshold too high or too low.

The alarm uses the 'Sum' statistic over a 60-second period and triggers when throttles exceed 5.

Practice

1. What does Lambda concurrency control in AWS Lambda functions?

easy

A. The total number of functions in an AWS account

B. The number of function instances that can run at the same time

C. The size of the function's deployment package

D. The amount of memory allocated to the function

Solution

1. Step 1: Understand Lambda concurrency concept

   Concurrency in Lambda means how many copies of your function can run simultaneously.

2. Step 2: Identify what concurrency controls

   It controls the number of function instances running at the same time to handle requests.

3. Final Answer:

   The number of function instances that can run at the same time -> Option B

4. Quick Check:

   Concurrency = simultaneous function runs [OK]

Hint: Concurrency = how many functions run at once [OK]

Common Mistakes:

• Confusing concurrency with memory size
• Thinking concurrency limits total functions
• Mixing concurrency with deployment package size

2. Which of the following is the correct way to set reserved concurrency for a Lambda function using AWS CLI?

easy

A. aws lambda update-function --name MyFunc --concurrency 5

B. aws lambda set-concurrency --function MyFunc --reserved 5

C. aws lambda put-function-concurrency --function-name MyFunc --reserved-concurrent-executions 5

D. aws lambda configure-concurrency --function MyFunc --limit 5

Solution

1. Step 1: Recall AWS CLI command for reserved concurrency

   The correct command is 'put-function-concurrency' with '--reserved-concurrent-executions' option.

2. Step 2: Match the correct syntax

   aws lambda put-function-concurrency --function-name MyFunc --reserved-concurrent-executions 5 matches the exact AWS CLI syntax to set reserved concurrency.

3. Final Answer:

   aws lambda put-function-concurrency --function-name MyFunc --reserved-concurrent-executions 5 -> Option C

4. Quick Check:

   Reserved concurrency CLI = put-function-concurrency [OK]

Hint: Use 'put-function-concurrency' with reserved count [OK]

Common Mistakes:

• Using wrong command names like 'set-concurrency'
• Incorrect option flags
• Confusing update-function with concurrency settings

3. Given a Lambda function with a reserved concurrency of 3, what happens if 5 requests arrive simultaneously?

medium

A. 3 requests run immediately; 2 are throttled and may be retried

B. All 5 requests run simultaneously without delay

C. Only 1 request runs; others are queued

D. All 5 requests are rejected immediately

Solution

1. Step 1: Understand reserved concurrency effect

   Reserved concurrency limits how many instances run at once; here it is 3.

2. Step 2: Analyze request handling

   When 5 requests come, 3 run immediately; the other 2 exceed limit and get throttled (rejected or retried).

3. Final Answer:

   3 requests run immediately; 2 are throttled and may be retried -> Option A

4. Quick Check:

   Requests > concurrency = throttling [OK]

Hint: Requests over concurrency limit get throttled [OK]

Common Mistakes:

• Assuming all requests run simultaneously
• Thinking requests queue automatically
• Believing throttled requests are dropped without retry

4. You set a reserved concurrency of 2 for a Lambda function but notice throttling errors even with only 2 requests at once. What is the likely cause?

medium

A. The reserved concurrency setting was not applied correctly

B. The account-level concurrency limit is lower than 2

C. The function timeout is set too high

D. The function's memory size is too small

Solution

1. Step 1: Check reserved concurrency application

   If throttling occurs at 2 requests, reserved concurrency might not be set or applied properly.

2. Step 2: Rule out other causes

   Memory size and timeout do not cause throttling; account limit lower than 2 is unlikely if 2 requests run.

3. Final Answer:

   The reserved concurrency setting was not applied correctly -> Option A

4. Quick Check:

   Throttling with low requests = misconfigured concurrency [OK]

Hint: Check if reserved concurrency is actually set [OK]

Common Mistakes:

• Blaming memory size for throttling
• Ignoring concurrency setting errors
• Assuming timeout causes throttling

5. You have two Lambda functions, A and B, sharing an account concurrency limit of 10. Function A has reserved concurrency 7. If both functions receive 7 simultaneous requests each, how many requests for function B will be throttled?

hard

A. 3 requests for function B will be throttled

B. 0 requests for function B will be throttled

C. 7 requests for function B will be throttled

D. 4 requests for function B will be throttled

Solution

1. Step 1: Understand reserved concurrency reservation

   Function A reserves 7 concurrency, so it can run up to 7 instances without throttling.

2. Step 2: Calculate remaining concurrency for function B

   Account limit is 10, so 10 - 7 = 3 concurrency left for function B.

3. Step 3: Analyze requests for function B

   Function B gets 7 requests but only 3 can run concurrently; 7 - 3 = 4 requests are throttled.

4. Final Answer:

   4 requests for function B will be throttled -> Option D

5. Quick Check:

   Reserved concurrency reduces available concurrency [OK]

Hint: Reserved concurrency reduces shared limit for others [OK]

Common Mistakes:

• Ignoring reserved concurrency reservation
• Assuming full account concurrency is available to all
• Miscounting throttled requests