Home / Engineering Blog / Zero RAM Leak Architecture

When you build a crawler for commercial data, you quickly realize that the real world does not look like clean demo websites. The real web is filled with 15-year-old ASP.NET pages with infinite redirects, bloated 40MB PDF catalogs linked on homepages, broken SSL handshakes, and aggressive Cloudflare rate limits.

Our initial prototype used a popular Python/Playwright stack. It worked smoothly on 10 websites. On 100 websites, it ate 2GB of RAM. At website #1,400, the Linux kernel OOM-killer mercilessly terminated the worker process.

The Diagnosis: Garbage Collection Laziness

Both Node.js (V8) and Python use generational garbage collectors optimized for quick throughput rather than immediate RAM surrender. When parsing large HTML trees into DOM nodes (using BeautifulSoup or Cheerio), thousands of string fragments remain allocated in memory pools. Even after closing the tab, the virtual memory allocator holds onto those heap pages.

The FlyCrawl Solution: Compiled Go & Aggressive FreeOSMemory

We rewrote the core crawler engine in Go (Golang). Here is why:

• Goroutine Lightweight Footprint: Each Go routine costs only ~2KB of stack space vs ~1MB for OS threads or Node container overhead.
• Direct OS Surrender: After completing a website crawl, we explicitly trigger a controlled GC pass with debug.FreeOSMemory() and set a strict memory ceiling with debug.SetMemoryLimit(128 * 1024 * 1024).
• HTTP Streaming Parser: Rather than building full browser DOM trees in memory, our Fit-Markdown extractor operates as a stream tokenizer, converting HTML tags to clean markdown on the fly.

This is why FlyCrawl is packaged as a lightweight, single-binary engine. It gives developers and AI teams cloud-scale extraction power without requiring bloated container infrastructure.

Experience the zero-leak difference today.

Get 100 free crawl credits and test your first URL in our playground.

Try FlyCrawl for Free 🚀