Propose a high-level system architecture. What services are needed?

The high-level system architecture depends on the task, but a general scheme for a scalable application may include the following services:

1. API Gateway — the entry point for clients, routes requests to internal services, implements authentication, rate limiting, and caching.

2. Authentication and Authorization Service — manages users, sessions, access rights.

3. Business Logic (microservices) — separate services implementing key system functions, such as order processing, product management, payments.

4. Database — stores data, can be relational or NoSQL, depending on requirements.

5. Queue/Message Service — for asynchronous task processing, integration between services (e.g., RabbitMQ, Kafka).

6. Caching — to speed up access to frequently used data (Redis, Memcached).

7. Monitoring and Logging — collection of metrics, logs, alerts for support and debugging.

8. Error Handling and DLQ Service — for handling failed messages and retries.

9. CI/CD Pipeline — automation of build, testing, and deployment.

10. UI/Frontend — web or mobile application interacting with the API Gateway.

Example: for an e-commerce platform, services such as catalogs, cart, payments, notifications, and analytics can be distinguished, each of which scales and develops independently.