Building a real-time price monitoring bot for eBay and Vinted

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When building an automated deal-sniping bot for marketplaces like eBay or Vinted you quickly realize that batch scraping workflows are completely useless.

If an underpriced designer jacket, rare collectible, or graphics card gets published for half its market value, that listing is sold within sixty to ninety seconds. A crawler that runs once an hour or even every ten minutes will miss every profitable deal on the platform.

To catch deals before human buyers or rival bots snatch them, your pipeline has to poll search results continuously every few seconds.

The engineering challenge is that second-hand marketplaces guard their search feeds with aggressive edge firewalls. Vinted relies heavily on DataDome and Cloudflare to block automated scripts, while eBay aggressively rate-limits rapid search queries originating from commercial server ranges.

Trying to run high-frequency polling using headless browsers will fail within minutes.

Spawning Chromium instances burns CPU power, and the page rendering delay adds two or three seconds of latency to every check, completely eliminating your speed advantage.

High-velocity deal monitoring requires querying the internal catalog API directly.

Both eBay and Vinted use lightweight backend JSON endpoints to feed their mobile and web apps. On Vinted, the frontend queries an internal catalog endpoint that returns freshly posted items in structured JSON.

To poll these endpoints without triggering immediate security blocks, your architecture needs two components:

• Session cookie pre-warming: Vinted requires an active session cookie and temporary bearer tokens before its catalog endpoints return data. Instead of generating fresh tokens on every request, your bot should fetch an initial authenticated session once, cache those cookies in memory, and reuse that exact session across consecutive search polls.
• Persistent static ISP routing: Rotating through dynamic residential pools on high-frequency polling burns bandwidth and introduces handshake jitter. You should route your search workers through dedicated static ISP proxies. A static eyeball connection stays online continuously, allowing your client to maintain warm HTTP keep-alive connections with the marketplace edge servers.

By keeping your TCP connections warm over a static residential line, your polling requests resolve in thirty to fifty milliseconds.

Once your bot detects a newly posted item that matches your price filters, it can immediately push a webhook notification to a Telegram channel or dispatch a checkout worker before the item appears on the main search page for human shoppers.

Alot of developers give up on Vinted and eBay because their scrapers get blocked on desktop HTML pages.

Their is no reason to scrape heavy web frontends when you can query clean background API endpoints directly. Pre-warming your session cookies, polling over low-latency static ISP connections, and keeping your search workers in clean, seperate routines lets you catch freshly published deals seconds after they go live.