Cloudflare recently published a deep dive on their official engineering blog detailing an impressive hyperscale achievement: without purchasing additional hardware or upgrading physical servers, their team reclaimed approximately 100 terabytes of RAM across their worldwide infrastructure.
The Math of Scale: Why Single Bytes Matter
Cloudflare’s public DNS resolver, 1.1.1.1, holds over 250 billion cache entries in memory at any given moment. When operating at this magnitude, the physics of software design shift dramatically:
A mere 1-byte overhead per cache entry translates to more than 250 gigabytes of wasted RAM across the global fleet.
Engineering Optimizations in the Rust Codebase
The underlying DNS caching engine—known internally as Big Pineapple—is written in Rust. By auditing memory allocations and struct layouts, engineers executed five targeted architectural changes:
- Replacing Dynamic Containers: Swapped dynamically sized types such as
VecandStringfor fixed-size boxed slices (Box<[T]>) to strip out unused capacity metadata on immutable cache data. - Buffer Flattening: Consolidated response buffers into unified blocks and indexed them using compact 2-byte offsets.
- De-duplicating Domain Names: Reconstructed domain names dynamically at read time instead of storing redundant string copies inside every entry.
- Raw Wire-Format Storage: Stored DNS payloads in their native, variable-length wire format rather than heavily padded custom structures.
Production Results
Once deployed globally across the edge fleet, the architectural refinements produced immediate operational gains:
- Decreased individual cache entry footprint from 953 bytes to 420 bytes (a 56% reduction).
- Freed approximately 100 TB of RAM—the hardware equivalent of roughly 130 modern 13th-generation servers.
- Increased cache insertion throughput by 43%.
- Reduced lookup latency by 19%.
For an in-depth breakdown of the code and benchmarks, read the full engineering report directly on the Cloudflare Blog.