Fjall Docs — Deploy Production-Ready AWS Infrastructure in Minutes

Overview

The Lambda Function resource provides serverless compute with automatic scaling, built-in high availability, and pay-per-use pricing. It covers both standard functions and singleton functions for AWS Custom Resources.

Resource Classes

import {
  LambdaFunction,
  SingletonFunction,
} from "@fjall/components-infrastructure/lib/resources/aws/compute/lambda";

Basic Usage

Standard Function

const lambda = new LambdaFunction(this, "MyFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: ["s3:GetObject"],
      resources: ["arn:aws:s3:::my-bucket/*"],
    }),
  ],
});

Singleton Function

const singleton = new SingletonFunction(this, "CustomResource", {
  code: Code.fromInline("exports.handler = async () => ({ statusCode: 200 })"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  uuid: "unique-function-id",
  inlinePolicy: [],
});

Configuration Options

Core Properties

Property	Type	Description	Default
`code`	`Code`	Function code source	Required
`handler`	`string`	Handler function	Required
`runtime`	`Runtime`	Lambda runtime	Required
`inlinePolicy`	`PolicyStatement[]`	IAM policy statements	Required

Function Configuration

Property	Type	Description	Default
`timeout`	`number`	Timeout in seconds	`300`
`memorySize`	`number`	Memory in MB (128-10240)	`128`
`ephemeralStorageSize`	`number`	Ephemeral storage in MiB	-
`architecture`	`Architecture`	CPU architecture	`x86_64`
`lambdaDescription`	`string`	Function description	`${id} Lambda`
`roleDescription`	`string`	IAM role description	-
`environment`	`KeyValue`	Environment variables	`{}`
`functionName`	`string`	Explicit function name	Auto-generated
`vpc`	`IVpc`	Place the function in a VPC	-
`logGroupRetention`	`RetentionDays`	Log retention period	`ONE_WEEK`

Function URL Configuration

Property	Type	Description	Default
`enableFunctionUrl`	`boolean`	Enable HTTP endpoint	`false`
`functionUrlAuthType`	`FunctionUrlAuthType`	Auth type	`AWS_IAM`
`functionUrlCors`	`FunctionUrlCorsOptions`	CORS configuration	-
`functionUrlInvokeMode`	`InvokeMode`	Invoke mode (use RESPONSE_STREAM for streaming)	-

Secrets Configuration

Property	Type	Description	Default
`secrets`	`string[]`	SSM Parameter Store secret names	-
`ssmSecretsPath`	`string`	Base path for SSM secrets	`/<appName>/lambda/<functionName>`
`secretsImport`	`Record<string, SecretImport>`	Secrets Manager imports	-

Code Sources

From Local Directory

const lambda = new LambdaFunction(this, "LocalCode", {
  code: Code.fromAsset("src/lambda"),
  handler: "app.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [],
});

From Inline Code

const lambda = new LambdaFunction(this, "InlineCode", {
  code: Code.fromInline(`
    exports.handler = async (event) => {
      console.log("Event:", JSON.stringify(event));
      return {
        statusCode: 200,
        body: JSON.stringify({ message: "Hello World" })
      };
    };
  `),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [],
});

From S3 Bucket

const lambda = new LambdaFunction(this, "S3Code", {
  code: Code.fromBucket(
    s3.Bucket.fromBucketName(this, "CodeBucket", "my-code-bucket"),
    "lambda-code.zip",
  ),
  handler: "main.handler",
  runtime: Runtime.PYTHON_3_11,
  inlinePolicy: [],
});

From Docker Image

const lambda = new LambdaFunction(this, "ContainerFunction", {
  code: Code.fromEcrImage(repository, {
    tag: "latest",
  }),
  handler: Handler.FROM_IMAGE,
  runtime: Runtime.FROM_IMAGE,
  inlinePolicy: [],
});

IAM Policies

The inlinePolicy property accepts an array of PolicyStatement objects. Each statement is added directly to the Lambda function’s execution role.

S3 Access

const lambda = new LambdaFunction(this, "S3Function", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: ["s3:GetObject", "s3:PutObject"],
      resources: [`${bucket.bucketArn}/*`],
    }),
  ],
});

DynamoDB Access

const lambda = new LambdaFunction(this, "DynamoFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: [
        "dynamodb:GetItem",
        "dynamodb:PutItem",
        "dynamodb:Query",
        "dynamodb:Scan",
      ],
      resources: [table.tableArn],
    }),
  ],
});

Multiple Policy Statements

const lambda = new LambdaFunction(this, "MultiPolicyFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: ["s3:GetObject"],
      resources: [`${bucket.bucketArn}/*`],
    }),
    new PolicyStatement({
      actions: ["dynamodb:Query"],
      resources: [table.tableArn],
    }),
    new PolicyStatement({
      actions: ["sqs:SendMessage"],
      resources: [queue.queueArn],
    }),
  ],
});

Environment Variables

const lambda = new LambdaFunction(this, "EnvFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  environment: {
    TABLE_NAME: dynamoTable.tableName,
    BUCKET_NAME: s3Bucket.bucketName,
    STAGE: "production",
  },
  inlinePolicy: [],
});

Function URL Configuration

Basic HTTP Endpoint

const lambda = new LambdaFunction(this, "HttpFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  enableFunctionUrl: true,
  functionUrlAuthType: FunctionUrlAuthType.NONE,
  inlinePolicy: [],
});

With CORS

const lambda = new LambdaFunction(this, "CorsFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  enableFunctionUrl: true,
  functionUrlAuthType: FunctionUrlAuthType.AWS_IAM,
  functionUrlCors: {
    allowedOrigins: ["https://example.com"],
    allowedMethods: [HttpMethod.GET, HttpMethod.POST],
    allowedHeaders: ["Content-Type", "Authorization"],
    maxAge: Duration.hours(1),
  },
  inlinePolicy: [],
});

Performance Configuration

High Memory Function

const mlFunction = new LambdaFunction(this, "MLFunction", {
  code: Code.fromAsset("lambda"),
  handler: "predict.handler",
  runtime: Runtime.PYTHON_3_11,
  memorySize: 10240, // Maximum: 10240 MB
  timeout: 900, // 15 minutes
  inlinePolicy: [
    new PolicyStatement({
      actions: ["s3:GetObject"],
      resources: ["arn:aws:s3:::ml-models/*"],
    }),
  ],
});

ARM Architecture

const lambda = new LambdaFunction(this, "ArmFunction", {
  code: Code.fromAsset("lambda"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  architecture: Architecture.ARM_64,
  inlinePolicy: [],
});

Event Sources

The LambdaFunction class provides three built-in event-source methods: addSqsEventSource, addDynamoDbEventSource, and addS3EventSource.

SQS Trigger

const processor = new LambdaFunction(this, "QueueProcessor", {
  code: Code.fromAsset("lambda"),
  handler: "queue.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: ["sqs:ReceiveMessage", "sqs:DeleteMessage"],
      resources: [queue.queueArn],
    }),
  ],
});

processor.addSqsEventSource(queue, {
  batchSize: 10,
  maxBatchingWindow: 30,
  reportBatchItemFailures: true,
});

DynamoDB Stream Trigger

const streamProcessor = new LambdaFunction(this, "StreamProcessor", {
  code: Code.fromAsset("lambda"),
  handler: "stream.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: [
        "dynamodb:GetRecords",
        "dynamodb:GetShardIterator",
        "dynamodb:DescribeStream",
        "dynamodb:ListStreams",
      ],
      resources: [`${table.tableArn}/stream/*`],
    }),
  ],
});

streamProcessor.addDynamoDbEventSource(table, {
  startingPosition: "LATEST",
  batchSize: 100,
  reportBatchItemFailures: true,
});

S3 Trigger

const fileProcessor = new LambdaFunction(this, "FileProcessor", {
  code: Code.fromAsset("lambda"),
  handler: "processor.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [
    new PolicyStatement({
      actions: ["s3:GetObject"],
      resources: [`${bucket.bucketArn}/*`],
    }),
  ],
});

fileProcessor.addS3EventSource(bucket, {
  events: ["OBJECT_CREATED"],
  filters: [{ prefix: "uploads/", suffix: ".csv" }],
});

Scheduling

The construct has no built-in scheduling method or prop. To run a function on a schedule, attach a standalone EventBridge Rule that targets the function.

import { Rule, Schedule } from "aws-cdk-lib/aws-events";
import { LambdaFunction as LambdaTarget } from "aws-cdk-lib/aws-events-targets";

const cleanup = new LambdaFunction(this, "DailyCleanup", {
  code: Code.fromAsset("lambda"),
  handler: "cron.handler",
  runtime: Runtime.NODEJS_20_X,
  inlinePolicy: [],
});

new Rule(this, "DailyCleanupSchedule", {
  schedule: Schedule.rate(Duration.days(1)),
  targets: [new LambdaTarget(cleanup)],
  description: "Daily cleanup job",
});

Singleton Function Pattern

Custom Resource Handler

const customResourceHandler = new SingletonFunction(
  this,
  "CustomResourceHandler",
  {
    uuid: "f7d4f730-4ee1-11e8-9c2d-fa7ae01bbebc",
    code: Code.fromInline(`
    const response = require("cfn-response");
    exports.handler = async (event, context) => {
      try {
        if (event.RequestType === "Delete") {
          // Cleanup logic
        } else {
          // Create/Update logic
        }
        await response.send(event, context, response.SUCCESS);
      } catch (error) {
        await response.send(event, context, response.FAILED);
      }
    };
  `),
    handler: "index.handler",
    runtime: Runtime.NODEJS_20_X,
    lambdaDescription: "Custom resource handler",
    inlinePolicy: [
      new PolicyStatement({
        actions: ["s3:ListBuckets"],
        resources: ["*"],
      }),
    ],
  },
);

Methods

Get Function URL

const url = lambda.getFunctionUrl();
// Returns: string | undefined (only when enableFunctionUrl is true)

Get Execution Role

const role = lambda.executionRole;
// Returns: IRole | undefined

Get Function ARN

const functionArn = lambda.functionArn;

Get Function Name

const functionName = lambda.functionName;

Outputs

The Lambda Function creates these CloudFormation outputs:

${id}FunctionArn - Function ARN
${id}FunctionUrl - Function URL (when enabled)

Complete Example

import { LambdaFunction } from "@fjall/components-infrastructure/lib/resources/aws/compute/lambda";
import { Code, Runtime } from "aws-cdk-lib/aws-lambda";
import { PolicyStatement } from "aws-cdk-lib/aws-iam";
import { FunctionUrlAuthType, HttpMethod } from "aws-cdk-lib/aws-lambda";

// Create Lambda function
const userApi = new LambdaFunction(this, "UserAPIFunction", {
  code: Code.fromAsset("src/lambda/user-api"),
  handler: "index.handler",
  runtime: Runtime.NODEJS_20_X,
  memorySize: 256,
  timeout: 30,
  environment: {
    TABLE_NAME: userTable.tableName,
    REGION: this.region,
  },
  enableFunctionUrl: true,
  functionUrlAuthType: FunctionUrlAuthType.AWS_IAM,
  functionUrlCors: {
    allowedOrigins: ["*"],
    allowedMethods: [
      HttpMethod.GET,
      HttpMethod.POST,
      HttpMethod.PUT,
      HttpMethod.DELETE,
    ],
    allowedHeaders: ["*"],
  },
  inlinePolicy: [
    new PolicyStatement({
      actions: [
        "dynamodb:GetItem",
        "dynamodb:PutItem",
        "dynamodb:UpdateItem",
        "dynamodb:DeleteItem",
        "dynamodb:Query",
      ],
      resources: [userTable.tableArn],
    }),
  ],
});

Tagging

The construct takes no tags prop. Apply tags through the CDK Tags aspect after construction.

import { Tags } from "aws-cdk-lib";

Tags.of(userApi).add("Environment", "production");
Tags.of(userApi).add("Application", "user-service");

Best Practices

Keep functions small and focused on single tasks
Use layers for shared dependencies
Set appropriate timeouts (not always the maximum)
Use environment variables for configuration
Use PolicyStatement arrays for least-privilege IAM
Consider ARM (Graviton2) for cost savings
Use secrets for sensitive values rather than environment variables

Performance Tips

Minimise package size to reduce cold starts
Reuse connections outside handler function
Use provisioned concurrency for predictable traffic
Choose appropriate memory (CPU scales with memory)
Maximum memory is 10240 MB (10 GB)

Next Steps

Compute Factory

Provision compute through the higher-level factory pattern.

IAM Role

Scope execution permissions for your function.

Messaging Factory

Create SQS queues to use as Lambda event sources.

Load Balancer

Front your function with an Application Load Balancer.

​Overview

​Resource Classes

​Basic Usage

​Standard Function

​Singleton Function

​Configuration Options

​Core Properties

​Function Configuration

​Function URL Configuration

​Secrets Configuration

​Code Sources

​From Local Directory

​From Inline Code

​From S3 Bucket

​From Docker Image

​IAM Policies

​S3 Access

​DynamoDB Access

​Multiple Policy Statements

​Environment Variables

​Function URL Configuration

​Basic HTTP Endpoint

​With CORS

​Performance Configuration

​High Memory Function

​ARM Architecture

​Event Sources

​SQS Trigger

​DynamoDB Stream Trigger

​S3 Trigger

​Scheduling

​Singleton Function Pattern

​Custom Resource Handler

​Methods

​Get Function URL

​Get Execution Role

​Get Function ARN

​Get Function Name

​Outputs

​Complete Example

​Tagging

​Best Practices

​Performance Tips

​Next Steps

Compute Factory

IAM Role

Messaging Factory

Load Balancer

Overview

Resource Classes

Basic Usage

Standard Function

Singleton Function

Configuration Options

Core Properties

Function Configuration

Function URL Configuration

Secrets Configuration

Code Sources

From Local Directory

From Inline Code

From S3 Bucket

From Docker Image

IAM Policies

S3 Access

DynamoDB Access

Multiple Policy Statements

Environment Variables

Function URL Configuration

Basic HTTP Endpoint

With CORS

Performance Configuration

High Memory Function

ARM Architecture

Event Sources

SQS Trigger

DynamoDB Stream Trigger

S3 Trigger

Scheduling

Singleton Function Pattern

Custom Resource Handler

Methods

Get Function URL

Get Execution Role

Get Function ARN

Get Function Name

Outputs

Complete Example

Tagging

Best Practices

Performance Tips

Next Steps