How a visitor goes from the catalogue to a paid order without the client ever being trusted for payment state.

1. 1A visitor browses the React storefront — catalogue, search and product detail — served from cached static assets behind Nginx
2. 2Adding items builds a cart; at checkout the client calls the API, which prices the order server-side
3. 3The backend creates a PayPal order server-side and returns it to the client to approve
4. 4On approval the backend captures and verifies the PayPal payment before the order is marked paid
5. 5A confirmation email is queued through Celery and the order is recorded against the customer's account

How a customer requests a bespoke handcrafted piece and it reaches the store for follow-up.

1. 1A customer opens the custom-orders page and describes the piece they want
2. 2The request is submitted to a token-authenticated endpoint and stored against their account
3. 3A notification email is dispatched to the store asynchronously through Celery
4. 4The store reviews and follows up, turning the request into a quote or an order

How every API call is authenticated, rate-limited and served — browser to bare metal, in milliseconds.

1. 1The React SPA calls the API over HTTPS; Nginx terminates TLS and proxies to Gunicorn
2. 2Django REST authenticates the token and checks the per-endpoint throttle counter in Redis
3. 3The view reads or writes orders and catalogue in PostgreSQL, using Redis for hot reads
4. 4The response returns quickly; any email or heavy work is handed to Celery off the request path

How a single git push rebuilds, redeploys and re-secures the entire containerised stack with no manual steps.

1. 1A push to main triggers the GitLab CI/CD pipeline, which builds a Docker image
2. 2The pipeline rsyncs the release over SSH to the VPS and runs docker compose up
3. 3Migrations and collectstatic run, then Nginx reloads with a Certbot-renewed TLS certificate
4. 4The new version is live in one flow — build, deploy, migrate and secure — end to end