Your serverless architecture using AWS API Gateway, AWS Lambda, and AWS DynamoDB experienced a large increase in traffic to a sustained 3000 requests per second, and the failure rates increased dramatically. The usage of your DynamoDB table did not exceed 50% of the provisioned throughput, and the primary key is also designed properly. What is the most likely reason to cause the issue?

Answer options:

A.Your API Gateway was throttling your requests.
B.Your AWS API Gateway was bottlenecking on request (de)serialization.
C.You did not request a limit increase on concurrent Lambda function executions.
D.The DynamoDB table was experiencing the semaphore lock.

Answer – C
Every Lambda function is allocated with a fixed amount of specific resources regardless of the memory allocation. Each function is allocated with a fixed amount of code storage per function and per account.
By default, AWS Lambda limits the total concurrent executions across all functions within a given region to 1000. 
For more information on Concurrent executions, please visit the below URL:
http://docs.aws.amazon.com/lambda/latest/dg/concurrent-executions.html