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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 a Pipe and Filter Text Processing Chain in Python

A functional pipe-and-filter chain that transforms text through uppercase, whitespace normalization, number removal, stopword filtering, and file export.

pipeline text-processing functional

Python

import re
import sys


def pipe_filter_chain(stream):
    def uppercase(text):
        return text.upper()

    def strip_whitespace(text):
        return " ".join(text.split())

    def remove_numbers(text):
        return re.sub(r"\d+", "", text)

    def remove_stopwords(text, stopwords={"the", "and", "of", "in"}):…

16 0 Open

System design patterns easy

How to Mock a Metrics Decorator in Python with unittest.mock

This code demonstrates a timing decorator that wraps a function to measure execution time and prints the duration, with a unit test using unittest.mock to patch the print function and assert it was called.

decorators unittest.mock metrics

Python

import time
from functools import wraps
from unittest.mock import patch

def add_metrics(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        result = func(*args, **kwargs)
        elapsed = time.perf_counter() - start
        print(f"{func.__name__} took {elapsed:.6f}s…

15 0 Open

System design patterns easy

Route Messages to Handlers with a Python Dict

This code demonstrates a simple message routing pattern using a dictionary to map topic keys to handler functions, with a default handler for unmatched topics.

routing dictionary message-broker

Python

def route_message(message, routing_table):
    """Route a message to the correct handler based on the topic key."""
    topic = message.get("topic", "default")
    handler = routing_table.get(topic, routing_table.get("default"))
    return handler(message)


def handle_orders(message):
    return f"Orders handler proc…

12 0 Open

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