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System design patterns

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

3 matches

How to Implement a Simple MVVM Binding Mock in Python

A minimal Python implementation of the MVVM pattern, mocking data binding so views auto-update when the view model changes.

mvvm binding observer pattern

Python

class BindingMock:
    def __init__(self, view_model):
        self.view_model = view_model
        self.subscribers = []

    def bind(self, property_name, callback):
        self.subscribers.append((property_name, callback))

    def set(self, property_name, value):
        setattr(self.view_model, property_name, va…

18 0 Open

System design patterns easy

How to Implement the Repository Pattern in Python with an In-Memory Dict

Stores, retrieves, updates, and deletes user records in memory using a Repository abstraction over a plain dict, isolating data access from business logic.

repository-pattern design-patterns in-memory

Python

class UserRepository:
    def __init__(self):
        self._storage = {}
        self._next_id = 1

    def create(self, name, email):
        user_id = self._next_id
        self._next_id += 1
        self._storage[user_id] = {"id": user_id, "name": name, "email": email}
        return self._storage[user_id]

    def…

11 0 Open

System design patterns medium

How to implement stale-while-revalidate caching in Python

A Python cache wrapper that returns a stale cached value with a fallback flag when the upstream fetch fails, using TTL-based freshness checks.

caching ttl resilience

Python

import time
from functools import lru_cache


class CachedService:
    def __init__(self, fetch_func, ttl=5):
        self.fetch_func = fetch_func
        self.ttl = ttl
        self._cache = {}
        self._timestamp = {}

    def get(self, key):
        now = time.time()
        if key in self._cache and now - self…

12 0 Open

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