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Database scaling & optimization

Indexing, connection pooling, read replicas, query tuning, and throughput-aware SQL.

4 matches

Approximate Count with HyperLogLog in Python

A mock HyperLogLog implementation uses hash-based registers to estimate cardinality of large datasets with sublinear memory.

hyperloglog cardinality hash

Python

import hashlib

class HyperLogLog:
    def __init__(self, precision=4):
        if precision < 4 or precision > 16:
            raise ValueError("precision must be between 4 and 16")
        self.precision = precision
        self.registers = [0] * (1 << precision)

    def _hash(self, value):
        return int(hashl…

14 0 Open

Database scaling & optimization easy

How to Count Star vs Estimate Matches in Python

Count how many times 'star' and 'estimate' annotations match their actual labels in a list of mock comparison results.

counting dictionary matching

Python

def count_star_vs_estimate(mock_scores):
    """
    Count the number of times 'star' wins and 'estimate' wins
    from a list of mock comparison results.

    Args:
        mock_scores: list of tuples, each (annotation, actual)
                     where annotation is 'star' or 'estimate'

    Returns:
        dict w…

12 0 Open

Database scaling & optimization easy

How to Mock a Function Call in Python with unittest.mock

Use unittest.mock.Mock to wrap a function and spy on its call count and arguments in Python.

mock unittest spy

Python

import random
from unittest.mock import Mock, patch


def select_n_plus_one(numbers: list[int]) -> int:
    """Return the first number that appears more than once, if any."""
    seen = set()
    for num in numbers:
        if num in seen:
            return num
        seen.add(num)
    return -1


def detect_mock(se…

14 0 Open

Database scaling & optimization easy

How to Shard Data by User ID Hash in Python

Deterministically map user IDs to shard indexes using an MD5 hash modulo the shard count in Python.

sharding hashing md5

Python

import hashlib

def shard_id(user_id: str, num_shards: int = 4) -> int:
    """Deterministically map a user_id to a shard index using MD5."""
    digest = hashlib.md5(user_id.encode("utf-8")).hexdigest()
    return int(digest[:8], 16) % num_shards

if __name__ == "__main__":
    user_ids = ["alice", "bob", "carol", "d…

12 0 Open

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