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System design patterns

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

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Builder pattern for mocking complex objects in Python

Use a fluent Builder to construct realistic mock objects with defaults, enabling readable test data setup.

class User:
    def __init__(self):
        self.name = "default"
        self.age = 0
        self.email = "unknown@example.com"
        self.address = "unknown"

    def __repr__(self):
        return f"User(name={self.name!r}, age={self.age}, email={self.email!r}, address={self.address!r})"


class UserBuilder:
   …

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System design patterns easy

How to Aggregate Mock API Routes by Method in Python

Groups mock API routes by path and method, collecting response bodies and counts into a nested dictionary structure.

defaultdict api-gateway aggregation

Python

from collections import defaultdict


def aggregate_mock_routes(routes):
    """Aggregate mock API routes by method and aggregate their response bodies."""
    aggregated = defaultdict(lambda: defaultdict(list))

    for route in routes:
        method = route["method"]
        path = route["path"]
        response = …

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System design patterns easy

How to Mock the Ambassador Pattern Retry Client in Python

This code demonstrates the ambassador pattern for API clients by simulating a flaky request and retrying with exponential backoff, useful for testing resilience in system design.

retry ambassador-pattern mock

Python

import time
import random


class RetryingClient:
    """Retry wrapper simulating a flaky ambassador-style API client."""

    def __init__(self, max_attempts=3, base_delay=0.1):
        self.max_attempts = max_attempts
        self.base_delay = base_delay
        self.attempts = 0

    def _flaky_request(self):
     …

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