Troubleshooting and Optimization

A developer deployed a new version of an AWS Lambda function that is part of a serverless application. The function uses an Amazon DynamoDB table as a data store. After deployment, the developer notices that the function's latency has increased significantly for some requests. CloudWatch traces show that the increase is due to DynamoDB throttle events. The function is configured with a reserved concurrency of 100 and the DynamoDB table has 5 read capacity units (RCUs) and 5 write capacity units (WCUs). What is the most effective way to reduce the throttling while maintaining application performance?

A developer is running an AWS Lambda function that is triggered by Amazon S3 events. The function writes processed data to an Amazon DynamoDB table. Over time, the function's execution time has increased significantly. CloudWatch Logs show many DynamoDBProvisionedThroughputExceededException errors. The table is configured with 5 read capacity units (RCUs) and 5 write capacity units (WCUs). The function performs both reads and writes. Which optimization will MOST effectively reduce throttling errors while maintaining performance?

A web application runs on Amazon EC2 instances behind an Application Load Balancer (ALB). During peak hours, users report receiving HTTP 503 (Service Unavailable) errors. The developer checks Amazon CloudWatch metrics and finds that the ALB's request count is high but below the limit, and the target group's healthy host count drops to zero intermittently. The Auto Scaling group for the instances is configured with a minimum of 2, maximum of 10, and a simple scaling policy to add 2 instances when CPU utilization exceeds 70% for 5 consecutive minutes. What is the most likely cause of the 503 errors?

A developer is troubleshooting an AWS Lambda function that processes large CSV files (up to 1 GB) uploaded to an Amazon S3 bucket. The function uses Python and the pandas library to perform data transformations. Recently, the function started timing out on large files. CloudWatch Logs show that the function's execution time is close to the 15-minute Lambda timeout, and memory utilization peaks at around 80% of the configured 3,008 MB. The function has not been modified in months. Which action will most likely resolve the timeout issue without requiring code changes?

A developer is troubleshooting an AWS Lambda function that is invoked from an Amazon S3 bucket via event notifications. The function processes images and stores metadata in Amazon DynamoDB. The developer notices that some images are being processed multiple times, resulting in duplicate entries in DynamoDB. The S3 event notification is configured to send events to the Lambda function with the 's3:ObjectCreated:*' event type. The function uses the 'uuid' library to generate a unique ID for each image upon processing. What is the most likely cause of the duplicate processing?

A developer is troubleshooting an AWS Lambda function that processes records from an Amazon Kinesis Data Stream. The function is configured with a batch size of 100 and a parallelization factor of 1. The developer notices that the function is processing records slowly, and the iterator age is increasing. CloudWatch Logs show that the function is not experiencing errors or throttling, but the execution time per invocation is close to the 5-minute timeout. The stream has 10 shards. What is the most cost-effective way to increase processing throughput?

A web application runs on Amazon EC2 instances behind an Application Load Balancer (ALB). During rolling updates of the Auto Scaling group, users intermittently receive HTTP 502 (Bad Gateway) errors. The developer checks the ALB access logs and notices that requests are being routed to instances that are in the 'Draining' state. The ALB has connection draining enabled with a timeout of 30 seconds. The Auto Scaling group terminates instances after they are taken out of service. What is the most likely cause of the 502 errors?

A developer notices that an AWS Lambda function, which processes messages from an SQS queue, is taking longer than expected. The function has a reserved concurrency of 5 and a batch size of 10. The SQS queue has a large backlog. CloudWatch metrics show that the function's throttles are high. The function is idempotent and can process up to 100 messages per invocation. What is the most effective way to increase throughput without increasing reserved concurrency?

An application running on Amazon ECS (Fargate) uses an Application Load Balancer (ALB) with connection draining enabled. The application is experiencing intermittent 502 (Bad Gateway) errors during rolling updates of the ECS service. The developer notices that the ALB is routing requests to tasks that are in the 'Draining' state. The ECS service is configured with a deployment circuit breaker that automatically rolls back a failed deployment. What is the most likely cause of the 502 errors?

A developer notices that an AWS Lambda function, which uses Amazon RDS Proxy to connect to an Aurora MySQL database, is experiencing increased latency and occasional connection timeouts. The function is configured with a reserved concurrency of 100 and is deployed in a VPC. The RDS Proxy's maximum connections is set to 1000. CloudWatch metrics show that the DatabaseConnections metric for the proxy is consistently at 1000. What is the most likely cause of the increased latency and timeouts?

A developer monitors an AWS Lambda function that processes records from an Amazon SQS queue and writes results to an Amazon DynamoDB table. CloudWatch Logs show that execution time has increased over the past week, and the function frequently times out at the 5-minute timeout. The function's code has not been changed recently. CloudWatch metrics show a high rate of DynamoDBProvisionedThroughputExceededException errors. The DynamoDB table has 5 write capacity units (WCUs). What action will MOST effectively reduce the function's execution time?

A developer is troubleshooting performance issues in an application that uses Amazon DynamoDB as the primary data store. The application reads a large set of items using a Query operation on a Global Secondary Index (GSI). The developer notices high read latency and throttled requests on the GSI. The base table has sufficient read capacity. The GSI is projected with KEYS_ONLY. Which action would most likely reduce the latency and throttling?

A developer monitors an AWS Lambda function that processes messages from an Amazon SQS queue. CloudWatch logs show that the function's execution time has increased significantly over the past week. The function's code has not been changed recently. The function makes calls to an Amazon DynamoDB table. CloudWatch metrics show a high rate of DynamoDBProvisionedThroughputExceededException errors. The DynamoDB table has 5 read and 5 write capacity units (RCU/WCU). What is the most effective action to reduce the function's execution time?

A developer is troubleshooting an AWS Lambda function that is triggered by an S3 event. The function occasionally fails with a timeout error. CloudWatch logs show that the timeout occurs during the processing of large files. The function has a memory setting of 128 MB and a timeout of 3 seconds. The developer wants to process large files without modifying the code. Which parameter should the developer adjust first?

A developer is troubleshooting performance issues in an application that uses Amazon ElastiCache for Redis. The application experiences periodic latency spikes during peak hours. The developer checks CloudWatch metrics and sees that the 'Evictions' metric is consistently high and the 'CacheHitRate' metric is low. The cluster uses a single cache.t3.small node. Which action will most likely improve the cache hit rate and reduce latency?

A developer is troubleshooting a DynamoDB table that is experiencing high write throttling (ProvisionedThroughputExceededException) on certain days. The table has provisioned write capacity of 1000 WCU. The table has a partition key of 'user_id' which is a UUID. The table is accessed by multiple services. CloudWatch metrics show that the WriteThrottleEvents are spiking during specific hours, and the ConsumedWriteCapacityUnits often reaches 1000. What is the most likely cause of the throttling?

A developer is troubleshooting an Amazon API Gateway REST API that returns 504 Gateway Timeout errors for certain requests. The backend is a Lambda function that performs a resource-intensive operation that occasionally takes up to 30 seconds. API Gateway has a default integration timeout of 29 seconds. The developer cannot reduce the execution time. What should the developer do to resolve the timeout issue?

A developer is troubleshooting an application that uses Amazon ElastiCache for Redis to improve performance. The application periodically experiences high latency during peak hours. The developer checks the ElastiCache metrics and sees that the 'Evictions' metric is consistently high and the 'CacheHitRate' metric is low. The cluster has a single node with a cache.t3.small instance type. Which action will most likely improve the cache hit rate and reduce latency?

An AWS Lambda function processes messages from an Amazon SQS queue and writes results to an Amazon DynamoDB table. The function is configured with a reserved concurrency of 5 and a batch size of 10. CloudWatch metrics show high throttling and a growing queue backlog. The function's execution time averages 1 second per message. What is the MOST effective action to reduce throttling while improving throughput?

A developer is debugging an issue where an Amazon S3 bucket policy is not allowing cross-account access for a user from another AWS account. The bucket policy grants access to the other account's root user. The IAM user in the other account has an IAM policy that allows s3:GetObject on the bucket. When the user tries to download an object, they get an Access Denied error. What is the most likely cause?

A developer has deployed an AWS Lambda function that is triggered by an Amazon S3 event. The function processes image files and stores metadata in an Amazon DynamoDB table. CloudWatch metrics show that the function's error count has increased. The developer checks CloudWatch Logs and sees errors related to insufficient memory. The function is configured with 128 MB of memory. What should the developer do to resolve the errors?

A developer is monitoring an AWS Lambda function that is triggered by an Amazon SQS queue. The function's CloudWatch metrics show a high number of throttles. The function has a reserved concurrency of 10 and the SQS queue has a large backlog of messages. The function processes each message in about 2 seconds and has a timeout of 60 seconds. Which action will most effectively reduce the throttles and increase throughput?

A developer is troubleshooting an AWS Lambda function that experiences high latency for the first few invocations after being idle. The function is written in Python and uses a large library (e.g., Pandas). The function connects to an RDS database in a VPC. What is the most effective way to reduce the latency for the first invocation after idle?

A developer notices that an AWS Lambda function, configured to access an Amazon RDS database in the same VPC, is timing out. The function has a 30-second timeout. CloudWatch Logs show that the function starts execution but never reaches the database. The VPC configuration includes private subnets without a NAT gateway. The RDS database is in the same VPC. What is the most likely cause of the timeout?

A developer notices that an AWS Lambda function processing S3 events is being retried frequently due to throttling errors from Amazon DynamoDB. The function writes records to a DynamoDB table and has reserved concurrency set to 100. The DynamoDB table uses on-demand capacity mode. What should the developer do to reduce retries and improve overall throughput?

A developer is managing an application running on Amazon EC2 instances behind an Application Load Balancer. Users report that the application becomes unresponsive after several hours, and restarting the instance temporarily fixes the issue. The developer suspects a memory leak but cannot add custom instrumentation. Which AWS service can collect memory utilization metrics and help identify the memory leak with minimal configuration?

A developer is troubleshooting an AWS Lambda function that processes records from an Amazon Kinesis Data Stream. The function is configured with a batch size of 100 and a parallelization factor of 1. The iterator age metric is increasing, and CloudWatch Logs show the function execution time is around 4 minutes (timeout is 5 minutes). The stream has 10 shards. What is the most cost-effective way to increase processing throughput?

A developer monitors an AWS Lambda function that processes messages from an Amazon SQS queue. CloudWatch logs show that the function's execution time has increased significantly over the past week, and it now frequently times out at the 5-minute timeout. The function's code has not been changed recently. The function makes calls to an Amazon DynamoDB table. What is the most likely cause of the increased execution time?

A developer is troubleshooting an AWS Lambda function that returns timeout errors when calling an external HTTPS API. The function is configured with a 30-second timeout and runs in a VPC with a public subnet and NAT Gateway. The developer checks CloudWatch logs and sees that the function is timing out at exactly 30 seconds. What is the most likely cause?

A DynamoDB application receives ProvisionedThroughputExceededException during predictable daily peaks. The workload is not cacheable. What should be changed?

Messages in an SQS queue are processed successfully but later reappear and are processed again. What is the most likely configuration issue?

A developer needs to trace a request across API Gateway, Lambda, and downstream AWS service calls. Which service should be enabled?

A Lambda function using a Kinesis event source repeatedly retries one bad record and blocks progress in the shard. Which feature helps isolate failed records after retry limits?

An API backed by Lambda returns high p95 latency after deployment. Which two telemetry sources are most useful first?

A DynamoDB table shows throttling on one partition key value. Which two signs point to a hot partition problem?

A Lambda function reading from Kinesis is falling behind. Which two metrics/settings should be reviewed first?

Users receive AccessDenied when downloading SSE-KMS encrypted S3 objects cross-account. Which two policies may need changes?

Drag and drop the steps to authenticate a user using Amazon Cognito User Pools in the correct order.

Match each AWS storage class to its description.

Match each AWS deployment strategy to its description.

A developer is troubleshooting a web application that intermittently returns HTTP 504 errors. The application runs on EC2 instances behind an Application Load Balancer. What is the most likely cause of these errors?

A Lambda function processing SQS messages is failing with concurrency errors. The function is configured with reserved concurrency of 5. The SQS queue has a batch size of 10. What is the most effective way to prevent throttling?

A company runs a monolithic application on EC2 Behind an Application Load Balancer. They want to migrate to a microservices architecture using ECS Fargate. What is the most important optimization to ensure minimal downtime during the migration?

A developer notices that an S3 bucket used for static website hosting returns 403 Forbidden for anonymous requests. The bucket policy allows s3:GetObject for Principal "*". What is the most likely issue?

A developer is optimizing a DynamoDB table for a gaming leaderboard. The table stores player scores and is read-heavy. Queries often fetch the top 10 scores. Which indexing strategy best reduces RCU consumption?

A company runs a stateful web application on EC2 instances in an Auto Scaling group. Users report that their session data is lost when instances are replaced during scaling events. What is the best solution to preserve session state?

A developer attaches the above bucket policy to an S3 bucket. An anonymous user tries to access https://my-bucket.s3.amazonaws.com/secret/key.txt. What is the result?

Which TWO actions can help reduce Lambda cold start times? (Choose two.)

A developer reports that an AWS Lambda function is timing out after 3 seconds. The function reads from an Amazon SQS queue. What is the most likely cause?

An application running on Amazon ECS with Fargate is experiencing high latency. The application writes logs to Amazon CloudWatch Logs. Which AWS service can be used to analyze the logs to pinpoint the cause of the latency?

A developer is troubleshooting an AWS CloudFormation stack that failed to create. The error message says 'The following resource(s) failed to create: [MyEC2Instance]'. What is the first step the developer should take?

An application running on Amazon ECS with Fargate is unable to pull an image from Amazon ECR. The task definition uses the 'default' task execution role. What is the most likely cause?

Refer to the exhibit. An IAM policy is attached to a user. The user tries to download an object from s3://my-bucket/secret/config.txt. What will happen?

A developer is using Amazon S3 to host a static website. The website returns 403 Forbidden errors. The bucket policy allows public read access. What is the most likely cause?

An application running on Amazon ECS Fargate is experiencing intermittent connection timeouts when calling an external API. The task has a public IP and a security group that allows outbound HTTPS. What is the most likely cause?

A developer is troubleshooting an AWS Lambda function that is triggered by an Amazon SQS queue. The function processes messages but occasionally fails. The failed messages are not being sent to the dead-letter queue (DLQ). What is the most likely reason?

Which TWO approaches can be used to optimize costs for an Amazon DynamoDB table with predictable read/write patterns? (Select TWO.)

A developer deployed a new version of a Lambda function that processes S3 events. After deployment, some S3 events are not being processed. The CloudWatch Logs show no errors. What is the most likely cause?

A developer is using AWS X-Ray to trace a Lambda function that calls DynamoDB and SQS. Some traces show errors. Which TWO actions should the developer take to diagnose the issue?

A developer is troubleshooting a slow RDS MySQL instance. Which TWO metrics in Amazon CloudWatch should the developer examine first?

Refer to the exhibit. A developer created this CloudFormation template. After deployment, the stack creation fails with 'Bucket name already exists'. What should the developer do to fix the issue?

Which TWO actions can help reduce the cold start time for an AWS Lambda function? (Choose 2)

A developer notices that an AWS Lambda function configured with a VPC is timing out when trying to access an Amazon S3 bucket. The function has the necessary IAM permissions. What is the most likely cause?

A developer is troubleshooting an AWS Elastic Beanstalk environment that is failing health checks. The environment runs a web application on Tomcat. The developer checks the logs and finds no errors. What is the most likely cause of the health check failure?

A developer is using Amazon DynamoDB for a new application. The developer wants to reduce read latency. Which design pattern should the developer use?

A developer is deploying a serverless application using AWS CloudFormation. The stack creation fails with the error 'CREATE_FAILED: The following resource(s) failed to create: [MyLambdaFunction]'. The developer checks the CloudFormation events and sees 'Resource creation cancelled'. What is the most likely cause?

A developer is troubleshooting a slow-performing Amazon RDS for MySQL database. Which TWO actions should the developer take to improve query performance?

A developer is using AWS X-Ray to trace requests through a microservices application. The developer notices that some traces are incomplete. Which TWO actions can help ensure complete traces?

A developer runs a script that uses the AWS CLI to copy a large number of files from an on-premises server to an S3 bucket. The copy operation fails partway through with a 'RequestTimeout' error. What is the MOST efficient way to resume the copy and ensure all files are transferred?

A developer is troubleshooting a slow-running query on an Amazon RDS for MySQL database. The query is used by a reporting application and takes over 30 seconds to complete. The database is a db.r5.large instance with 200 GB of gp2 storage. Which TWO actions should the developer take to improve query performance?

A company is running a serverless application using AWS Lambda and Amazon API Gateway. The application experiences increased latency during peak hours. CloudWatch metrics show that Lambda function duration remains stable, but API Gateway latency spikes. Which THREE actions should the developer take to reduce API Gateway latency?

A developer is deploying a new microservice on AWS Elastic Beanstalk. The service uses an RDS database. The developer wants to ensure that database credentials are not stored in the application's source code. Which TWO methods should the developer use to securely provide credentials to the application?

A company runs a critical application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application experiences intermittent errors where some requests return HTTP 503 (Service Unavailable) errors. The developers have verified that the application code is healthy and the EC2 instances pass health checks. The ALB health check is configured to hit a specific endpoint (/health) with a healthy threshold of 2 and an unhealthy threshold of 2. The health check interval is 30 seconds, and the timeout is 5 seconds. The application's /health endpoint sometimes takes up to 6 seconds to respond due to a dependency on a third-party service. The developers want to minimize the 503 errors without changing the application code. Which action should the developer take?

A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). Users report intermittent 503 errors. The ALB health checks are failing for a few instances, but the instances themselves are running and have healthy application processes. What is the MOST likely cause?

A developer is optimizing a Node.js Lambda function that processes CSV files from S3. The function reads the entire file into memory, processes it, and writes results to DynamoDB. For large files, the function runs out of memory. What is the MOST effective optimization?

A developer notices that an S3 bucket policy allows public read access to all objects. The bucket contains sensitive data that should only be accessible by authorized IAM users. What is the BEST way to remediate this?

A developer is troubleshooting a slow-running Amazon RDS for PostgreSQL instance. Which TWO metrics should the developer examine in Amazon CloudWatch to identify a possible resource bottleneck?

A company is using Amazon S3 to store log files. The logs are rarely accessed after 30 days but must be retained for 7 years for compliance. Which THREE actions should the company take to optimize storage costs?

A developer receives an AccessDenied error when trying to put an object into an S3 bucket using the AWS SDK. The IAM user has an attached policy that grants s3:PutObject on the bucket. What is the MOST likely cause of the error?

An application running on Amazon EC2 instances behind an Application Load Balancer (ALB) is experiencing intermittent 503 errors. The EC2 instances are in an Auto Scaling group. What is the MOST likely cause?

A company is using Amazon API Gateway to expose a REST API. The API is integrated with an AWS Lambda function. Lately, the API is returning 502 Bad Gateway errors. What is the MOST likely cause?

A developer is using Amazon DynamoDB with provisioned throughput. The application is receiving ProvisionedThroughputExceededException errors. What is the BEST way to handle this error?

A developer is deploying a new version of an AWS Lambda function using the AWS CLI. The deployment fails with a 'ResourceConflictException' error. What is the MOST likely cause?

A developer is troubleshooting an AWS Lambda function that times out when processing large files from Amazon S3. The function has a 15-minute timeout and 512 MB memory. What should the developer do to resolve this issue?

A developer deploys a new version of an AWS Lambda function using the AWS CLI. After deployment, the function returns stale results. What is the most likely cause?

A company's application uses Amazon DynamoDB as its database. The application reads the same item multiple times per second and occasionally sees stale data. The DynamoDB table uses the default eventually consistent reads. What should the developer change to ensure strongly consistent reads?

A company's application runs on Amazon EC2 instances in an Auto Scaling group. The application experiences intermittent failures, and the developer suspects the application is not properly handling termination notifications. Which TWO steps should the developer take to diagnose the issue?

An application running on EC2 instances behind an Application Load Balancer (ALB) occasionally returns HTTP 503 errors. The instances are in an Auto Scaling group. Which action should be taken to resolve this issue?

A developer is deploying a new version of a Lambda function using an alias for blue/green deployment. Traffic is gradually shifted to the new version. During the shift, a high error rate is observed. What should the developer do to minimize impact?

A company uses AWS CodePipeline with CodeBuild to test and deploy a web application. The pipeline has been failing at the deploy stage with an error: 'Access Denied'. CloudTrail shows the CodePipeline service role is making the call. What is the MOST likely cause?

A developer has deployed a serverless application using AWS SAM. After a recent update, the API Gateway endpoints return 500 errors. The Lambda function logs show no errors. What should the developer investigate first?

A developer notices that an AWS Lambda function is timing out after 3 seconds. The function processes messages from an SQS queue. What is the MOST likely cause of the timeout?

A developer configured an S3 bucket to trigger a Lambda function on object creation. The Lambda function processes the object and then deletes it. Some objects are not being processed. What should the developer do to ensure all objects are processed?

A developer is using AWS Elastic Beanstalk to deploy a web application. The application is experiencing high latency. Which TWO steps should the developer take to troubleshoot and optimize the application?

A company is using Amazon S3 to store large objects. Users report that uploads are slow. Which THREE actions should the developer take to optimize upload performance?

A developer notices that an Amazon RDS for MySQL DB instance's CPU utilization is consistently above 90% during peak hours. The application uses read-heavy workloads. Which action would MOST effectively reduce CPU load without major architectural changes?

A developer is troubleshooting a CloudFormation stack that fails to create. The stack includes an Auto Scaling group with a launch template. The error message says 'Value (null) for parameter groupId is invalid.' What is the MOST likely cause?

A developer is trying to decrypt an S3 object using an AWS KMS key. The decryption fails with an 'AccessDenied' error. The IAM policy attached to the developer's user includes the statement in the exhibit. The KMS key policy includes the following statement: { "Sid": "Enable IAM User Permissions", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::123456789012:root" }, "Action": "kms:*", "Resource": "*" } What is the most likely reason for the failure?

A developer is debugging an application that uses Amazon SQS. The application occasionally processes the same message twice. Which TWO configurations can help prevent duplicate processing?

A web application running on EC2 instances behind an Application Load Balancer (ALB) is experiencing intermittent 503 errors. The ALB target group health checks are succeeding. Which step should the developer take FIRST to diagnose the issue?

A developer is using Amazon RDS for MySQL and notices that the database performance has degraded. The developer suspects that slow queries are the cause. Which THREE actions should the developer take to identify and address the slow queries?