Weight Loss Plan

Weight Loss Plan helps make healthier food choices, set weight loss goals to helps users get more active and burn more calories.

The app follows the standard pattern. It uses a Static Assets S3 bucket to pull information using its “Calorie Search” function. The name of this bucket is hardcoded into the mobile app which makes replacing it more difficult.

Architecture Overview

graph TD;
    User[User Request]
    CloudFront[CloudFront CDN]
    S3Media[S3 Media Bucket]
    StaticAssets[S3 StaticAssets Bucket]
    ALB[Application Load Balancer]
    ECS[ECS Fargate - Django CMS/API]
    RDS[Aurora PostgreSQL]
    OpenSearch[Amazon OpenSearch]
    Firebase[Firebase / Push Services]
    SurveyMonkey[SurveyMonkey API]
    Secrets[Secrets Manager / SSM]

    User --> CloudFront --> S3Media
    User --> CloudFront --> StaticAssets
    User --> ALB --> ECS --> RDS
    ECS --> OpenSearch
    ECS --> S3Media
    ECS --> Firebase
    ECS --> SurveyMonkey
    ECS --> Secrets

Components

Applications

• Repo: weightloss-cms-iac – Django CMS for the app.

Infrastructure as Code

• Repo: weightloss-iac – Terraform modules that infrastructure.

Environments

Environment	URL	Notes
Production	https://weightloss-cms-prod.phedigital.co.uk	Static assets served from https://cdn.weightloss-cms-prod.phedigital.co.uk.
Staging	https://weightloss-cms-stg.phedigital.co.uk	Mirrors production integrations; CDN https://cdn.weightloss-cms-stg.phedigital.co.uk.
Dev	https://weightloss-cms-dev.phedigital.co.uk	First landing-zone account; CDN https://cdn.weightloss-cms-dev.phedigital.co.uk.

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DNS Overview

Every environment manages two Route 53 hosted zones inside its AWS account: one for the CMS hostname (weightloss-cms-<env>.phedigital.co.uk) that ALIASes the environment’s ALB, and one for the CDN hostname (cdn.<env>.weightloss.phedigital.co.uk) that ALIASes the CloudFront distribution (issued out of us-east-1). The root phedigital.co.uk zone in the phe-prd account delegates both hostnames to the environment accounts.

Subdomains:

• weightloss-cms-prd.phedigital.co.uk / -stg / -dev – CMS and API entrypoints (ALB).
• cdn.weightloss-cms-prod.phedigital.co.uk / cdn.weightloss-cms-stg.phedigital.co.uk / cdn.weightloss-cms-dev.phedigital.co.uk – CloudFront distributions that front the S3 media bucket.

graph TD
  subgraph PHE_PRD[phedigital.co.uk – phe-prd account]
    ROOT[phedigital.co.uk Root Zone]
  end

  subgraph DEV_ACC[dev account]
    DEV_CMS[weightloss-cms-dev.phedigital.co.uk]
    DEV_CDN[cdn.weightloss-cms-dev.phedigital.co.uk]
    ALB_DEV[ALB - dev]
    CF_DEV[CloudFront - dev]
  end

  subgraph STG_ACC[stg account]
    STG_CMS[weightloss-cms-stg.phedigital.co.uk]
    STG_CDN[cdn.weightloss-cms-stg.phedigital.co.uk]
    ALB_STG[ALB - stg]
    CF_STG[CloudFront - stg]
  end

  subgraph PRD_ACC[prd account]
    PRD_CMS[weightloss-cms-prd.phedigital.co.uk]
    PRD_CDN[cdn.weightloss-cms-prod.phedigital.co.uk]
    ALB_PRD[ALB - prd]
    CF_PRD[CloudFront - prd]
  end

  ROOT -->|NS| DEV_CMS
  ROOT -->|NS| STG_CMS
  ROOT -->|NS| PRD_CMS
  ROOT -->|NS| DEV_CDN
  ROOT -->|NS| STG_CDN
  ROOT -->|NS| PRD_CDN

  DEV_CMS --> ALB_DEV
  STG_CMS --> ALB_STG
  PRD_CMS --> ALB_PRD

  DEV_CDN --> CF_DEV
  STG_CDN --> CF_STG
  PRD_CDN --> CF_PRD

If a hosted zone is recreated, update the NS entries held in the phe-prd root zone so delegation stays correct.