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1.1 AWS Lambda

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AWS Certified Developer – Associate DVA-C02

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1 Introduction: DVA-C02 Overview & Study Plan

1.1 What the AWS Developer Associate Tests 1.2 Exam Format, Scoring & Logistics 1.3 The Four Domains & A Study Plan

2 Chapter 1: Development with AWS Services

1.1 AWS Lambda 1.2 Amazon API Gateway 1.3 Amazon DynamoDB 1.4 Amazon S3 1.5 Messaging: SQS, SNS, EventBridge 1.6 Containers: ECS, ECR, Fargate 1.7 AWS SDK & API Best Practices

3 Chapter 2: Security

2.1 IAM for Developers 2.2 Encryption & AWS KMS 2.3 Secrets Manager vs Parameter Store 2.4 Amazon Cognito

4 Chapter 3: Deployment

3.1 CloudFormation & SAM 3.2 CI/CD with CodePipeline, CodeBuild, CodeDeploy 3.3 Deployment Strategies 3.4 Elastic Beanstalk & Container Deploys

5 Chapter 4: Troubleshooting, Optimization & Exam Strategy

4.1 Observability: CloudWatch & X-Ray 4.2 Performance & Caching 4.3 Common Traps & Final Review

1.1 AWS Lambda

Key Takeaways Explain This Topic AI

Lambda's maximum function timeout is 900 seconds (15 minutes); ephemeral /tmp storage is configurable from 512 MB up to 10,240 MB (10 GB), and memory ranges 128 MB to 10,240 MB.

Synchronous (RequestResponse) payloads are capped at 6 MB request and response; asynchronous (Event) event payloads are capped at 1 MB.

Reserved concurrency caps and isolates a function's concurrent executions; provisioned concurrency pre-warms execution environments to remove cold-start latency.

A version is an immutable snapshot of code plus configuration; an alias is a movable pointer to a version that supports weighted (canary) traffic shifting.

Asynchronous invocations are retried twice by default; exhausted events go to a dead-letter queue (DLQ) or an on-failure destination instead of being silently dropped.

Last updated: October 2026

Why Lambda Dominates the Exam

AWS Lambda is serverless compute that runs your code in response to events, billed per request and per GB-second of compute (rounded to 1 ms). It is the single most-tested service on the AWS Certified Developer - Associate (DVA-C02) exam, which carries 65 questions in 130 minutes with a scaled passing score of 720 out of 1,000. Development with AWS Services is 32% of the scored content, and Lambda anchors it. Most items are scenario-based: which limit did you hit , how does concurrency behave under a traffic spike , or which invocation model retries on your behalf .

Handler, Context, and the Execution Environment

Every function has a handler — the entry point Lambda calls once per event. The handler receives an event object (the payload) and a context object holding invocation metadata such as aws_request_id , function_name , and get_remaining_time_in_millis() . Code placed outside the handler (the initialization phase) runs once per execution environment, so create SDK clients, open database connections, and load config there to reuse them across warm invocations. A classic trap: opening a new database connection inside the handler exhausts connection pools under load.

The Three Invocation Models

  • Model Caller waits? Retries Payload limit Example source
  • Synchronous (RequestResponse) Yes Caller's job 6 MB request + response API Gateway, ALB, SDK Invoke
  • Asynchronous (Event) No 2 retries (default) 1 MB S3, SNS, EventBridge
  • Poll-based (event source mapping) N/A Per source Batch-based SQS, Kinesis, DynamoDB Streams

For poll-based sources, Lambda itself polls and forms batches — you do not write the polling loop. With SQS, set the function reserved concurrency and batch size carefully; with Kinesis and DynamoDB Streams, ordering is preserved per shard and a poison record can block the shard unless you configure bisectBatchOnFunctionError or a failure destination.

Configuration Building Blocks

Environment variables pass configuration and are encrypted at rest with an AWS KMS key. Layers package shared libraries or a custom runtime; a function attaches up to five layers , and the unzipped function plus all layers must stay under the 250 MB deployment quota. Need bigger artifacts? Package the function as a container image up to 10 GB. Versions are immutable snapshots of code and configuration ( $LATEST is mutable); aliases are named, movable pointers to a version. Aliases support weighted routing — send 10% of traffic to a new version for a canary deployment, then shift to 100%.

Concurrency, Cold Starts, and Limits

Reserved concurrency sets a fixed ceiling for one function, both guaranteeing that capacity and fencing the function so a noisy neighbor cannot drain the account's default 1,000 concurrent-execution pool. Provisioned concurrency keeps a set number of environments pre-initialized and warm, eliminating cold-start latency for predictable traffic. A cold start is the time to download code, start the runtime, and run init code. Memorize these hard limits:

  • Limit Value
  • Max timeout 900 s (15 min)
  • Memory 128 MB - 10,240 MB
  • /tmp ephemeral storage 512 MB - 10,240 MB
  • Sync payload (req + resp) 6 MB
  • Async event payload 1 MB
  • Layers per function 5
  • Unzipped package + layers 250 MB
  • Container image size 10 GB
  • Default account concurrency 1,000

CPU scales with memory: allocating more memory proportionally raises vCPU, so a CPU-bound function can finish faster (and sometimes cheaper) at higher memory. AWS Lambda Power Tuning is the standard tool to find the cost/performance sweet spot.

Error Handling and DLQs

For asynchronous invocations, Lambda retries a failed event twice (three total attempts) with delays, then discards it unless you capture it. Configure a dead-letter queue (an SQS queue or SNS topic) or, preferably, an on-failure destination (which can also be EventBridge or another Lambda and includes richer context). For poll-based SQS, failed messages return to the queue and move to the source queue's DLQ after maxReceiveCount . Never assume an async failure surfaces to the original caller — it does not.

Networking and Observability

By default a function runs in an AWS-managed VPC with internet access. Attach it to your VPC only when it must reach private resources (an RDS database, an internal NLB), and remember that such a function then loses default internet access — give it a NAT gateway or VPC endpoints for AWS APIs. Lambda automatically emits logs to Amazon CloudWatch Logs (one log group per function), publishes metrics such as Invocations , Errors , Throttles , Duration , and ConcurrentExecutions , and integrates with AWS X-Ray for distributed tracing when active tracing is enabled.

A spike in the Throttles metric, not Errors , is the signal that you hit a concurrency limit and should raise reserved/account concurrency rather than debug code.

Common Exam Traps

Confusing reserved (a ceiling that also reserves capacity) with provisioned (pre-warmed environments) concurrency — they solve different problems.

Forgetting that the 6 MB synchronous limit covers both the request and the response combined.

Assuming $LATEST is safe to point production aliases at — promote to an immutable version instead.

Initializing clients inside the handler, defeating connection reuse across warm starts.