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System design patterns

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

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How to Build an Immutable Money Value Object in Python

Implement an immutable Money class with rounded decimal amounts, currency, safe equality, and hashing for use as a value object.

value-object immutability money

Python

class Money:
    def __init__(self, amount: float, currency: str):
        object.__setattr__(self, "_amount", round(amount, 2))
        object.__setattr__(self, "_currency", currency)

    def __setattr__(self, name, value):
        raise AttributeError(f"Money is immutable: cannot set '{name}'")

    def __delattr__…

13 0 Open

System design patterns medium

How to Limit Concurrent Requests with a Semaphore in Python

Use threading.Semaphore with a ThreadPoolExecutor to cap how many worker threads run simultaneously, preventing resource overload.

concurrency semaphore threading

Python

import threading
import time
from concurrent.futures import ThreadPoolExecutor

def worker(name, semaphore, results):
    with semaphore:
        results.append(f"start {name}")
        time.sleep(0.5)  # simulate async work
        results.append(f"done {name}")

def main():
    sem = threading.Semaphore(2)  # max 2 …

14 0 Open

System design patterns medium

Implement Bulkhead Thread Pool Isolation in Python

Create isolated thread pools with a bulkhead pattern to protect different services from cascading failures.

bulkhead threadpool concurrency

Python

import threading
import time
import random
from concurrent.futures import ThreadPoolExecutor


class Bulkhead:
    """Simple bulkhead isolation: separate thread pools for different tasks."""

    def __init__(self, max_workers):
        self.executor = ThreadPoolExecutor(max_workers=max_workers)
        self.active = …

13 0 Open

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