Build a Price Monitoring System on Liquid Web

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A self-hosted price monitoring system on Liquid Web needs a scraper, storage, a scheduler, and alerting. This guide outlines the architecture and implementation options.

For managed price monitoring without running servers, Apify offers Actors for Amazon, Google Shopping, and e-commerce sites.

System Architecture

Component	Role	Options
Scraper	Fetch prices from target sites	Playwright, Apify Actor, Firecrawl
Storage	Persist historical prices	PostgreSQL, SQLite
Queue	Optional job queue	Redis, Bull/BullMQ
Scheduler	Run scraper on interval	cron, node-cron
Alerting	Notify on price drops	Email, Slack, webhook

cron (hourly)  →  Scraper  →  PostgreSQL
                     ↓
              Redis (optional queue)
                     ↓
              Alert if price < threshold  →  Email/Slack

Recommended VPS Specs

Volume	RAM	Storage	Liquid Web Plan
10–50 products	4 GB	80 GB	$8.50/mo
100–500 products	8 GB	240 GB	$22.50/mo
1000+ products	16 GB	440 GB	$45/mo

Pricing verified June 2026. Plans change frequently — check the vendor’s official pricing page for current rates.

See Liquid Web VPS for current plans.

Step 1: Database Schema

CREATE TABLE products (
  id SERIAL PRIMARY KEY,
  url TEXT UNIQUE NOT NULL,
  name TEXT,
  target_price DECIMAL(10,2),
  created_at TIMESTAMPTZ DEFAULT NOW()
);

CREATE TABLE price_history (
  id SERIAL PRIMARY KEY,
  product_id INT REFERENCES products(id),
  price DECIMAL(10,2) NOT NULL,
  scraped_at TIMESTAMPTZ DEFAULT NOW()
);

CREATE INDEX idx_price_history_product ON price_history(product_id);
CREATE INDEX idx_price_history_scraped ON price_history(scraped_at);

Step 2: Scraper Options

Option A: Playwright (self-hosted)

// Minimal price extraction
const { chromium } = require('playwright');
const price = await page.locator('.price').textContent();

Deploy via Docker or bare VPS.

Option B: Apify Actor

Use Apify Store (e.g. Amazon Scraper, Google Shopping). Call via API from your cron job. Apify handles proxies and anti-bot.

Option C: Firecrawl

Firecrawl returns markdown. Parse with regex or LLM for structured price extraction.

Step 3: Scheduler (Cron)

# Run scraper every hour
0 * * * * cd /home/user/price-monitor && node scraper.js >> /var/log/price-monitor.log 2>&1

Or use node-cron inside a long-running Node process for finer control.

Step 4: Alerting

When current_price <= target_price:

• Email — Nodemailer, SendGrid, or Resend
• Slack — Incoming webhook
• Make.com — Webhook trigger → email/Slack/other actions

Docker Compose Stack

services:
  scraper:
    build: .
    env_file: .env
    depends_on:
      - postgres
      - redis

  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: pricemonitor
      POSTGRES_USER: scraper
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    volumes:
      - pgdata:/var/lib/postgresql/data

  redis:
    image: redis:alpine

volumes:
  pgdata:

When to Use Apify Instead

• Anti-bot targets — Amazon, Walmart, etc. Apify manages proxies and rotation.
• Many domains — Different selectors per site. Apify Store has pre-built Actors.
• Low ops preference — No servers to maintain.

Apify price monitoring Actors can feed data to your PostgreSQL via webhook or scheduled API calls.

Next step

Start with 5–10 products and a simple Playwright scraper. Add alerting once the pipeline is stable.

Frequently Asked Questions

Scraper (Playwright or Apify) + PostgreSQL for history + cron for scheduling + email/Slack for alerts when price drops below threshold.

Yes. Use a VPS (e.g. Liquid Web), run scraper + DB + cron. Apify is the managed alternative.

Scraper (Playwright/Apify), database (PostgreSQL), scheduler (cron), alerting (email/Slack). For complex sites, add proxies.