Which algorithm has logarithmic complexity O(log n)?

The difference in scope and testing points of isolation:

Monolithic architecture:

• Testing covers one large application.
• Types of testing include system testing at the whole application level, regression testing across the entire monolith, and end-to-end testing simulating external interactions.
• Dependencies are high between modules within the application. Changes in one part can affect others.
• Deployment is a single unit. Testing focuses on one artifact.
• Tools are standard for web apps, API, databases.
• Debugging is simpler within one process.

Microservices architecture:

• Each microservice is tested in isolation, then their interaction is tested.
• Types include unit testing, component testing, integration testing, end-to-end testing, and contract testing.
• Dependencies are low between services. Contract and integration testing at service boundaries are crucial.
• Deployment involves multiple independent units. CI/CD pipelines are critical.
• Tools for distributed systems, API testing, monitoring.
• Debugging is more complex, requiring distributed tracing.

Parameter	Monolith	Microservices
Testing scope	Whole application	Individual services + their interaction
Dependencies	Internal, within codebase	Network-based, between services
Test data	Centralized	Managed per service, considering dependencies
Integration	Module-level	Service-to-service, contract testing
Fault tolerance	Less critical at module level	Critical at service boundaries

Example contract test with Pact:

// pact_broker/pacts/consumer-provider/latest.json
{
  "consumer": {"name": "MyConsumer"},
  "provider": {"name": "MyProvider"},
  "interactions": [
    {
      "description": "Get user by ID",
      "request": {
        "method": "GET",
        "path": "/users/123",
        "headers": {"Accept": "application/json"}
      },
      "response": {
        "status": 200,
        "headers": {"Content-Type": "application/json"},
        "body": {"id": 123, "name": "John Doe"}
      }
    }
  ],
  "metadata": {
    "pactRust": {"version": "1.0.0"},
    "pactSpec": {"version": "3.0.0"}
  }
}

This JSON describes a contract where the consumer expects a GET request to /users/123 and a response with status 200 and a JSON body. The consumer generates this contract, and the provider verifies it.

This ensures API compatibility and reduces integration issues.