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System design patterns

Sharding, load balancing, CAP tradeoffs, and scaling patterns — interview and production ready.

4 matches

Facade Pattern in Python with Mock Simplification

This code demonstrates the Facade pattern by hiding complex subsystem interactions behind a simple start/stop interface, and adds a MockFacade for testing failure scenarios.

facade-pattern design-patterns abstraction

Python

class SubsystemA:
    def operation_a(self):
        return "Subsystem A: ready"

class SubsystemB:
    def operation_b(self):
        return "Subsystem B: ready"

class SubsystemC:
    def operation_c(self):
        return "Subsystem C: ready"


class Facade:
    def __init__(self):
        self._a = SubsystemA()
   …

15 0 Open

System design patterns medium

How to Implement Retry with Exponential Backoff and Jitter in Python

This code demonstrates a retry mechanism with exponential backoff and optional full jitter, using a flaky mock network call for testing.

retry backoff jitter

Python

import random
import time


def retry_with_backoff(func, max_attempts=5, base_delay=0.1, jitter=True):
    """
    Retry a function with exponential backoff and optional full jitter.
    """
    for attempt in range(max_attempts):
        try:
            return func()
        except Exception as e:
            if att…

14 0 Open

System design patterns medium

How to Mock a Timeout per Dependency Call in Python

This code demonstrates how to simulate and test per-call timeouts for external dependencies using Python's unittest.mock and a simple timing wrapper.

mock timeout unittest

Python

```python
import time
from unittest.mock import Mock, patch

def call_dependency(dependency, timeout):
    start = time.time()
    result = dependency.call()
    elapsed = time.time() - start
    if elapsed > timeout:
        raise TimeoutError(f"Dependency call took {elapsed:.2f}s, exceeding timeout {timeout}s")
    …

14 0 Open

System design patterns medium

Mock Unit of Work commit and rollback in Python

Verify that a Unit of Work pattern commits on success and rolls back on failure using unittest.mock in Python.

unit-of-work mocking testing

Python

from unittest import mock


class UnitOfWork:
    def __init__(self):
        self.committed = False
        self.rolled_back = False

    def commit(self):
        self.committed = True
        print("Commit executed")

    def rollback(self):
        self.rolled_back = True
        print("Rollback executed")


def b…

13 0 Open

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