System design patterns
Sharding, load balancing, CAP tradeoffs, and scaling patterns — interview and production ready.
Circuit Breaker Pattern in Python: Closed, Open, and Half-Open States
Implement a circuit breaker with closed, open, and half-open states to prevent repeated calls to failing services and allow recovery after a timeout.
class CircuitBreaker:
def __init__(self, failure_threshold=3, timeout_seconds=5):
self.failure_threshold = failure_threshold
self.timeout_seconds = timeout_seconds
self.state = "closed"
self.failure_count = 0
self.last_failure_time = None
def record_success(self):
…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.
```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")
…Browse by section
Each section groups closely related Python snippets.
System design patterns — Python code examples
What you will find here
This page collects system design patterns snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.
Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.