[AWS] Story 2: Data Layer (Aurora + Redis)

[mfittko]

Summary

Implement the data layer: Aurora PostgreSQL Serverless v2 for persistent storage and ElastiCache Redis for caching and event bus.

Epic: #174
Architecture: docs/architecture/planned/aws-ecs-cdk.md

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Tasks

Aurora PostgreSQL Serverless v2

• Create Aurora cluster with Serverless v2 capacity
• Configure min/max ACU (default: 0.5-4)
• Enable encryption at rest (KMS)
• Configure automatic backups (7 days retention)
• Store credentials in Secrets Manager (auto-generated)
• Create database security group (ECS access only)

ElastiCache Redis

• Create Redis cluster (single node, t4g.micro default)
• Enable encryption in transit (TLS)
• Enable encryption at rest
• Configure auth token in Secrets Manager
• Create Redis security group (ECS access only)

Application Prerequisites

• Verify LLM Proxy supports rediss:// URL scheme (TLS Redis)
• Document connection string format for Aurora

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Configuration Props

// Aurora
auroraMinCapacity?: number;  // default: 0.5 ACU
auroraMaxCapacity?: number;  // default: 4 ACU
auroraBackupRetention?: number; // default: 7 days

// Redis  
redisNodeType?: string;      // default: cache.t4g.micro
redisNumNodes?: number;      // default: 1

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Acceptance Criteria

• Aurora cluster deploys with Serverless v2
• Redis cluster deploys with TLS enabled
• Credentials stored in Secrets Manager
• Security groups restrict access to ECS only
• cdk deploy completes successfully

Note: Migration testing moves to Story 3 (Compute) since we need ECS to connect to the private database.

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Dependencies

• Story 1: CDK Foundation (VPC, security groups)

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Estimated Effort

Medium - 2 days

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Notes

• Aurora Serverless v2 scales to 0.5 ACU (~$43/month base)
• Redis t4g.micro is ~$12/month
• Database connectivity testing happens in [AWS] Story 3: Compute Layer (ECS Fargate) #178 (Compute Layer)