リアルタイム不正検知 / リスクスコアリング（リスク管理）

import * as cdk from "aws-cdk-lib";
import { Construct } from "constructs";
import * as kinesis from "aws-cdk-lib/aws-kinesis";
import * as lambda from "aws-cdk-lib/aws-lambda";
import { KinesisEventSource } from "aws-cdk-lib/aws-lambda-event-sources";
import * as dynamodb from "aws-cdk-lib/aws-dynamodb";
import * as sns from "aws-cdk-lib/aws-sns";
import * as events from "aws-cdk-lib/aws-events";
import * as s3 from "aws-cdk-lib/aws-s3";

// ストリーム駆動：Kinesis → Lambda(特徴量/スコア) → DynamoDB、EventBridge→SNS、生イベントはS3。
// API Gateway は使いません（取引イベントのストリーム取込が入口）。
export class FraudDetectionStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const stream = new kinesis.Stream(this, "TxnStream", { shardCount: 2 });

    const scores = new dynamodb.Table(this, "Scores", {
      partitionKey: { name: "txnId", type: dynamodb.AttributeType.STRING },
      billingMode: dynamodb.BillingMode.PAY_PER_REQUEST,
    });

    const lake = new s3.Bucket(this, "EventLake", {
      encryption: s3.BucketEncryption.S3_MANAGED,
      enforceSSL: true,
      blockPublicAccess: s3.BlockPublicAccess.BLOCK_ALL,
    });

    const alerts = new sns.Topic(this, "Alerts");
    const bus = new events.EventBus(this, "RiskBus");

    const scorer = new lambda.Function(this, "Scorer", {
      runtime: lambda.Runtime.NODEJS_20_X,
      handler: "index.handler",
      code: lambda.Code.fromInline("exports.handler = async () => ({ ok: true });"),
      environment: { SCORES: scores.tableName, LAKE: lake.bucketName, ALERTS: alerts.topicArn, BUS: bus.eventBusName },
    });
    scorer.addEventSource(new KinesisEventSource(stream, { batchSize: 100, startingPosition: lambda.StartingPosition.LATEST }));
    scores.grantWriteData(scorer);
    lake.grantWrite(scorer);
    alerts.grantPublish(scorer);
    // NOTE: SageMaker 推論エンドポイント呼び出し（sagemaker:InvokeEndpoint）を scorer のロールに付与します。
  }
}