Я строю системы, которые заменяют ручную работу.

<?php
declare(strict_types=1);

// Webhook нового заказа: подпись → валидация → БД → уведомление.
// Секреты берутся из окружения, в коде их нет.

$secret  = getenv('ORDER_WEBHOOK_SECRET') ?: '';
$payload = file_get_contents('php://input');
$given   = $_SERVER['HTTP_X_SIGNATURE'] ?? '';

if (!hash_equals(hash_hmac('sha256', $payload, $secret), $given)) {
    http_response_code(401);
    exit;
}

$order = json_decode($payload, true, 8, JSON_THROW_ON_ERROR);

$rules = [
    'id'     => fn($v) => is_int($v) && $v > 0,
    'phone'  => fn($v) => preg_match('/^\+?\d{10,15}$/', (string) $v),
    'items'  => fn($v) => is_array($v) && count($v) > 0,
    'total'  => fn($v) => is_numeric($v) && $v >= 0,
];
foreach ($rules as $field => $ok) {
    if (!isset($order[$field]) || !$ok($order[$field])) {
        http_response_code(422);
        echo json_encode(['error' => "invalid {$field}"]);
        exit;
    }
}

$db = Db::connection();
$db->beginTransaction();
try {
    $db->prepare(
        'INSERT INTO orders (id, phone, total, status, created_at)
         VALUES (:id, :phone, :total, "new", NOW())
         ON DUPLICATE KEY UPDATE total = VALUES(total)'
    )->execute([
        'id' => $order['id'], 'phone' => $order['phone'], 'total' => $order['total'],
    ]);

    $stmt = $db->prepare('INSERT INTO order_items (order_id, sku, qty) VALUES (?, ?, ?)');
    foreach ($order['items'] as $item) {
        $stmt->execute([$order['id'], $item['sku'], (int) $item['qty']]);
    }
    $db->commit();
} catch (Throwable $e) {
    $db->rollBack();
    error_log('order webhook: ' . $e->getMessage());
    http_response_code(500);
    exit;
}

// Уведомление — асинхронно, чтобы не держать вебхук открытым.
Queue::push('telegram.notify', [
    'chat' => 'orders',
    'text' => sprintf("🛒 Заказ #%d — %s ₴\n%d позиций",
        $order['id'], number_format($order['total'], 0, '.', ' '), count($order['items'])),
]);

http_response_code(202);
echo json_encode(['ok' => true]);

"""Мониторинг цен: обход по расписанию, история, AI-оценка изменений."""
from __future__ import annotations

import asyncio
import logging
from dataclasses import dataclass
from decimal import Decimal

import httpx
from tenacity import retry, stop_after_attempt, wait_exponential

from monitor.db import PriceRepo
from monitor.llm import classify_change
from monitor.notify import telegram

log = logging.getLogger(__name__)


@dataclass(frozen=True)
class Target:
    sku: str
    url: str
    selector: str


@retry(stop=stop_after_attempt(4), wait=wait_exponential(min=2, max=30))
async def fetch_price(client: httpx.AsyncClient, target: Target) -> Decimal:
    resp = await client.get(target.url, timeout=20)
    resp.raise_for_status()
    node = parse_html(resp.text).select_one(target.selector)
    if node is None:
        raise LookupError(f"selector miss: {target.sku}")
    return normalize_price(node.get_text())


async def check(target: Target, repo: PriceRepo, client: httpx.AsyncClient) -> None:
    price = await fetch_price(client, target)
    previous = await repo.last(target.sku)
    await repo.append(target.sku, price)

    if previous is None or previous == price:
        return

    delta = (price - previous) / previous * 100
    verdict = await classify_change(target.sku, previous, price, delta)
    if verdict.significant:
        await telegram.send(
            "pricing",
            f"📉 {target.sku}: {previous} → {price} ({delta:+.1f}%)\n{verdict.reason}",
        )


async def main() -> None:
    repo = PriceRepo.from_env()
    targets = await repo.targets()
    sem = asyncio.Semaphore(6)  # не долбим один сайт параллельно

    async with httpx.AsyncClient(headers={"User-Agent": "price-monitor/2.1"}) as client:
        async def guarded(t: Target) -> None:
            async with sem:
                try:
                    await check(t, repo, client)
                except Exception:  # одна ошибка не должна ронять весь прогон
                    log.exception("target failed: %s", t.sku)

        await asyncio.gather(*(guarded(t) for t in targets))


if __name__ == "__main__":
    asyncio.run(main())

// Тонкий API-клиент: дедупликация одинаковых запросов,
// отмена устаревших, оптимистичное обновление кэша.

const inflight = new Map();

export function createClient({ baseUrl, onError }) {
  const cache = new Map();

  async function request(method, path, { body, signal } = {}) {
    const key = method === 'GET' ? `GET ${path}` : null;
    if (key && inflight.has(key)) return inflight.get(key);

    const run = fetch(baseUrl + path, {
      method,
      headers: { 'Content-Type': 'application/json' },
      body: body ? JSON.stringify(body) : undefined,
      signal,
    })
      .then(async (res) => {
        if (!res.ok) throw new ApiError(res.status, await res.text());
        return res.status === 204 ? null : res.json();
      })
      .catch((err) => {
        if (err.name !== 'AbortError') onError?.(err);
        throw err;
      })
      .finally(() => key && inflight.delete(key));

    if (key) inflight.set(key, run);
    return run;
  }

  return {
    get: (path, opts) => request('GET', path, opts),

    // Оптимистично: UI видит изменение сразу, откат — только при ошибке.
    async patch(path, body, { optimistic } = {}) {
      const prev = cache.get(path);
      if (optimistic) cache.set(path, { ...prev, ...body });
      try {
        const data = await request('PATCH', path, { body });
        cache.set(path, data);
        return data;
      } catch (err) {
        cache.set(path, prev);
        throw err;
      }
    },

    // Поиск с отменой предыдущего запроса при новом вводе.
    search: (() => {
      let controller;
      return (q) => {
        controller?.abort();
        controller = new AbortController();
        return request('GET', `/search?q=${encodeURIComponent(q)}`, {
          signal: controller.signal,
        });
      };
    })(),
  };
}

export class ApiError extends Error {
  constructor(status, body) {
    super(`API ${status}`);
    this.status = status;
    this.body = body;
  }
}