cdk-infrastructure-queues

CDK Infrastructure

Overview

AWS CDK (Cloud Development Kit) enables infrastructure-as-code in TypeScript. This guide covers production-ready patterns for real estate Lambda applications.

Note: As of 2025, the CDK CLI and Construct Library have separate version lines. The CLI uses 2.1000+ numbering; the construct library (e.g. aws-cdk-lib) continues 2.x (e.g. 2.238+). Both work together—use aws-cdk-lib@^2.238.0 and the latest CLI.

Project Structure

cdk/
├── bin/
│   └── app.ts                    # CDK app entry point
├── lib/
│   ├── stacks/
│   │   ├── api-stack.ts          # API Gateway + Lambda handlers
│   │   ├── messaging-stack.ts    # SNS, SQS, retry queues
│   │   ├── data-stack.ts         # DynamoDB, RDS, OpenSearch
│   │   └── monitoring-stack.ts   # CloudWatch, alarms
│   └── constructs/
│       ├── sqs-retry-ladder.ts   # Reusable retry queue pattern
│       ├── lambda-function.ts    # Standard Lambda configuration
│       └── dynamodb-table.ts     # Table with GSIs
├── cdk.json
├── tsconfig.json
└── package.json

Dependencies

pnpm add -D aws-cdk-lib constructs @types/node esbuild

SQS Retry Ladder Pattern

Construct Definition

// cdk/lib/constructs/sqs-retry-ladder.ts

import { Construct } from "constructs";
import { Duration, RemovalPolicy } from "aws-cdk-lib";
import { Queue, DeadLetterQueue } from "aws-cdk-lib/aws-sqs";

export interface RetryLadderProps {
  /**
   * Base name for the queues
   */
  queueName: string;
  
  /**
   * Delay configuration for each retry tier
   */
  retryDelays?: {
    tier1Seconds: number;
    tier2Seconds: number;
    tier3Seconds: number;
  };
  
  /**
   * Max receive count before moving to next tier
   */
  maxReceiveCount?: number;
  
  /**
   * Message retention period
   */
  retentionPeriod?: Duration;
  
  /**
   * Visibility timeout for processing
   */
  visibilityTimeout?: Duration;
}

export class SqsRetryLadder extends Construct {
  public readonly mainQueue: Queue;
  public readonly retryQueue1: Queue;
  public readonly retryQueue2: Queue;
  public readonly retryQueue3: Queue;
  public readonly deadLetterQueue: Queue;

  constructor(scope: Construct, id: string, props: RetryLadderProps) {
    super(scope, id);

    const retryDelays = props.retryDelays ?? {
      tier1Seconds: 30,
      tier2Seconds: 300, // 5 minutes
      tier3Seconds: 1800, // 30 minutes
    };
    const maxReceiveCount = props.maxReceiveCount ?? 3;
    const retentionPeriod = props.retentionPeriod ?? Duration.days(14);
    const visibilityTimeout = props.visibilityTimeout ?? Duration.seconds(30);

    // Dead Letter Queue (final destination for failed messages)
    this.deadLetterQueue = new Queue(this, "DLQ", {
      queueName: `${props.queueName}-dlq`,
      retentionPeriod: Duration.days(14),
      removalPolicy: RemovalPolicy.RETAIN,
    });

    // Retry Queue 3 → DLQ
    this.retryQueue3 = new Queue(this, "RetryQueue3", {
      queueName: `${props.queueName}-retry-3`,
      deliveryDelay: Duration.seconds(retryDelays.tier3Seconds),
      visibilityTimeout,
      retentionPeriod,
      deadLetterQueue: {
        queue: this.deadLetterQueue,
        maxReceiveCount,
      },
    });

    // Retry Queue 2 → Retry Queue 3
    this.retryQueue2 = new Queue(this, "RetryQueue2", {
      queueName: `${props.queueName}-retry-2`,
      deliveryDelay: Duration.seconds(retryDelays.tier2Seconds),
      visibilityTimeout,
      retentionPeriod,
      deadLetterQueue: {
        queue: this.retryQueue3,
        maxReceiveCount,
      },
    });

    // Retry Queue 1 → Retry Queue 2
    this.retryQueue1 = new Queue(this, "RetryQueue1", {
      queueName: `${props.queueName}-retry-1`,
      deliveryDelay: Duration.seconds(retryDelays.tier1Seconds),
      visibilityTimeout,
      retentionPeriod,
      deadLetterQueue: {
        queue: this.retryQueue2,
        maxReceiveCount,
      },
    });

    // Main Queue → Retry Queue 1
    this.mainQueue = new Queue(this, "MainQueue", {
      queueName: props.queueName,
      visibilityTimeout,
      retentionPeriod,
      deadLetterQueue: {
        queue: this.retryQueue1,
        maxReceiveCount,
      },
    });
  }

  /**
   * Returns all queue URLs as environment variables
   */
  public getEnvironmentVariables(): Record<string, string> {
    return {
      MAIN_QUEUE_URL: this.mainQueue.queueUrl,
      RETRY_QUEUE_1_URL: this.retryQueue1.queueUrl,
      RETRY_QUEUE_2_URL: this.retryQueue2.queueUrl,
      RETRY_QUEUE_3_URL: this.retryQueue3.queueUrl,
      DLQ_URL: this.deadLetterQueue.queueUrl,
    };
  }
}