Saving 100 terabytes of memory by optimizing 1.1.1.1's DNS cache

8 relevance

Cloudflare's DNS cache optimization is a deep technical post on memory optimization directly relevant to infrastructure engineering.

Cloud blog.cloudflare.com

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Why It Matters

For a platform engineer focused on infrastructure efficiency, this demonstrates how a low-level Rust type change at massive scale yields both dramatic memory savings and performance gains, a pattern directly applicable to any high-throughput caching or data-plane service.

Key Takeaways

Audit your hot-path data structures for unused capacity overhead (Vec, String) and replace with fixed-size slices (Box<[T]>, Box<str>) when entries are immutable after creation.

Saving 100 terabytes of memory by optimizing 1.1.1.1's DNS cache

Summary

Cloudflare's Big Pineapple DNS cache, storing over 250 billion entries across 1.1.1.1 and other services, was consuming excessive memory due to Rust's Vec and String capacity overhead. By switching to Box<[T]> and Box<str>, which eliminate unused capacity fields and heap reservation, the per-entry footprint dropped over 50%, freeing 100 TB of fleet memory—equivalent to 130 Gen 13 servers. The optimization also improved performance: insert throughput rose 43% and lookup latency fell 19%, as fewer allocations and better memory locality avoided the typical space-speed tradeoff.