4.7 KiB
4.7 KiB
``` md
## Immediate
User registers: AuthService saves the user and emits a UserSignedUpEvent.
Listener catches it: The WelcomeEmailListener hears the event.
Queue handles it: The listener adds a job to BullMQ called send-welcome-email.
Worker processes it: A separate background worker picks up the job, tries to send the email, and automatically handles retries if it fails.
2. Also an API of my own
3. Production and testing env diff
# 🏗️ SaaS Architect’s Roadmap: NestJS & DevOps
This document serves as a strategic guide for evolving from a developer to an architect. It balances the "What" (the technology) with the "How" (the engineering mindset).
---
## 🛠️ Phase 1: The "What" — Advanced Backend Features
*Focus: Scaling complexity and ensuring production-grade reliability.*
### 1. Advanced Multi-Tenancy Architecture
* **The Goal:** Move beyond simple `organization_id` filters to true data isolation.
* **Concepts:** Shared Database/Separate Schema or **Row Level Security (RLS)**.
* **Challenge:** Implement a NestJS `Interceptor` or `Provider` that extracts a `tenant_id` from the request and automatically switches the database context/schema.
### 2. Background Tasks & Reliability
* **The Goal:** Decouple time-consuming tasks from the request/response cycle.
* **Tech Stack:** **BullMQ** + **Redis**.
* **Implementation:** Offload email invitations, image processing, and report generation to a separate "Worker" instance.
### 3. Real-Time Interactions
* **The Goal:** Create a reactive, living dashboard.
* **Tech Stack:** **Socket.io** (WebSockets).
* **Implementation:** Sync team membership changes or notification counts in real-time without requiring a page refresh.
### 4. Billing & Webhooks (The SaaS "S")
* **The Goal:** Turn a project into a business.
* **Tech Stack:** **Stripe API**.
* **Learning Point:** Handle **Idempotency**. Ensure that if Stripe sends a "Payment Success" webhook twice, you only upgrade the user's account once.
---
## 🧠 Phase 2: The "How" — Architectural Thinking
*Focus: Designing systems that don't break under edge cases.*
### 1. State Machine Logic
Stop thinking in "CRUD" (Create, Read, Update, Delete) and start thinking in **Transitions**.
* **Entity Lifecycle:** An Invitation isn't just a row; it's a flow: `Pending` → `Accepted` | `Declined` | `Expired`.
* **Action:** Explicitly define what happens during every status change (e.g., "On Accept: Create User, Join Team, Clear Invite Cache").
### 2. Atomic Transactions
Never perform "partial" updates.
* **Strategy:** Use Database Transactions (`BEGIN...COMMIT`) for any operation touching multiple tables. If the user joins the team but the invitation update fails, the whole thing must roll back.
### 3. Event-Driven Side Effects
Don't bloat your services with 10 different tasks.
* **Pattern:** Use an **Event Emitter**.
* **Logic:** `UserService.create()` emits a `USER_CREATED` event. Separate listeners then handle the email, the analytics ping, and the Slack notification independently.
---
## ☁️ Phase 3: The DevOps Pillar
*Focus: Automation, Observability, and "Infrastructure as Code".*
### 1. Observability (Stop Guessing)
* **Structured Logging:** Use **Pino** to output JSON logs that include `trace_id` and `tenant_id`.
* **Tracing:** Implement **OpenTelemetry** to visualize the lifecycle of a request across different services.
### 2. Infrastructure as Code (IaC)
* **The Goal:** Destroy and rebuild your entire cloud environment in minutes.
* **Tech Stack:** **Terraform**.
* **Action:** Codify your GCP/Azure VMs, VPC Firewalls, and Managed Databases so you never have to click buttons in a portal manually.
### 3. Hardened CI/CD
* **The Goal:** Catch errors before they hit production.
* **Action:** Add "Structure Verification" steps in your GitHub Actions to ensure the build folder matches what the server expects (e.g., checking for Next.js standalone chunks).
---
## 🤖 The "Anti-GIGO" AI Workflow
*How to use AI as an architect, not a typist.*
1. **Sketch First:** Define your DB schema and logic flow on a whiteboard before opening the chat.
2. **Hunt Edge Cases:** Ask yourself: "What if the user is already in another org? What if the database is locked?"
3. **Prompt as an Architect:**
* *Bad:* "Make an invite system."
* *Good:* "Design a NestJS service for an Invitation State Machine. It must use a database transaction, handle BullMQ for email side-effects, and include a unique constraint on (email, organization_id)."
4. **Audit the Output:** Check for N+1 query problems, lack of input validation, and missing error handling.
---
**Next Steps for You:**
* Start with the **Invitation State Machine**.
* Implement **BullMQ** for the invitation email.
* Write your first **Terraform** script to manage your GCP firewall.