Architecting Production Backend Systems

When asked to build a service (e.g., "build a Go/Python/Node order-processing service with Postgres and Pub/Sub"), immediately produce, in this order:

1. Repository tree (markdown, └── syntax)
2. Every file, each starting with a path comment on line 1
3. No prose between code blocks beyond a one-line section header

Example first output block:

# Repository Structure
.
├── cmd/
│   └── server/
│       └── main.go
├── internal/
│   ├── api/
│   ├── domain/
│   ├── repository/
│   └── observability/
├── deploy/
│   ├── terraform/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   └── outputs.tf
│   ├── Dockerfile
│   └── cloudbuild.yaml
├── .env.example
├── .gitignore
├── go.mod
└── README.md

Then emit each file in full, starting with:

Go
// cmd/server/main.go
package main
...

Progress checklist for every service build:

• Clarify runtime (language/framework), datastore, and messaging boundaries from the request — infer sane Google-stack defaults if unstated (Go or Python, Postgres via Cloud SQL, Pub/Sub, Redis for cache)
• Emit repository tree
• Emit domain layer: entities + validation (Pydantic/Zod/struct tags), explicit typed error values
• Emit repository/data layer: connection pool config (min/max conns, idle timeout), retry wrapper with exponential backoff + jitter, migrations
• Emit service/business logic layer: circuit breaker wrapping all external calls, context propagation, timeout budgets
• Emit transport layer (HTTP/gRPC): input validation, structured error responses, correlation ID middleware, /healthz (liveness), /readyz (readiness including dependency pings)
• Emit observability: structured JSON logger, trace ID injection, Prometheus/OpenTelemetry metric hooks
• Emit graceful shutdown handling (SIGTERM drain, in-flight request completion, pool close)
• Emit config layer: env-var driven, validated at boot, fail-fast on missing required vars
• Emit Dockerfile: multi-stage, distroless/alpine final stage, non-root user, minimal attack surface
• Emit cloudbuild.yaml (or GitHub Actions) with lint → test → build → scan → deploy stages
• Emit Terraform: main.tf, variables.tf, outputs.tf — VPC, IAM least-privilege service accounts, autoscaling compute (Cloud Run/GKE), Secret Manager bindings
• Emit .env.example, .gitignore, lint config (.golangci.yml/ruff.toml/.eslintrc)
• Emit dependency manifest with pinned versions
• Emit README.md last: architecture rationale, local run, test commands, deploy pipeline
• Silently self-verify every checklist item is fully implemented before final output — fix gaps without narrating the check