Cloudflare Reclaims 100 Terabytes of Fleet Memory by Overhauling 1.1.1.1 DNS Cache Layout

Cloudflare has reclaimed roughly 100 terabytes of memory across its global infrastructure without swapping a single physical server module. The massive memory saving stems entirely from software optimizations made to the DNS cache of Big Pineapple, the internal platform powering the 1.1.1.1 public resolver, Gateway DNS, and DNS Firewall^[2].

According to a technical disclosure published on the Cloudflare Blog by systems engineer Sebastiaan Neuteboom, the engineering team applied five successive Rust data structure optimizations to the DNS cache layout. The changes cut the average size of a cached DNS entry from 953 bytes to 420 bytes, achieving a 56 percent reduction in memory footprint. Instead of trading performance for memory density, the streamlined layout increased cache insertion throughput by 43 percent and reduced lookup latency by 19 percent^[2].

The Multiplier Effect of Operating at Massive Scale

The scale of Cloudflare's recursive DNS operations makes even microscopic software inefficiencies expensive. In its technical breakdown, Cloudflare revealed that Big Pineapple maintains more than 250 billion cached DNS entries across its fleet at any given time. Operating at that volume means that wasting just a single byte per entry wastes more than 250 gigabytes of RAM across the fleet.

Reporting on the initiative, Tom's Hardware noted that reclaiming 100 terabytes of RAM is equivalent to the entire memory capacity of 130 of Cloudflare's 768-gigabyte Gen 13 servers. This hardware efficiency arrives at a time when server-grade DDR5 memory prices face upward pressure from AI data center demand^[1].

At that scale, wasting a single byte per entry costs more than 250 gigabytes of memory across our fleet.

Sebastiaan Neuteboom, Systems Engineer at Cloudflare

Five Key Rust Optimizations Behind the Memory Reduction

The engineering team achieved the 56 percent reduction through five targeted refinements to their Rust memory layout:

• Replacing growable collections with boxed slices: Standard Rust containers like Vec and String carry capacity metadata to allow dynamic growth. Because DNS entries become immutable once cached, Cloudflare switched to fixed-size Box<[T]> and Box<str> types, eliminating 64 bytes per entry and saving over 15 terabytes across the fleet^[1].
• Consolidating record sections: DNS responses typically separate records into answer, authority, and additional sections. Cloudflare merged these into a single contiguous buffer indexed by compact two-byte offsets, reducing vector and pointer overhead.
• Eliminating duplicate domain names: Many cached response records redundantly duplicate the queried domain name. Engineers removed these duplicate owner fields from stored entries and rebuilt them at read time instead^[1].
• Boxing large enum variants: In Rust, an enum is sized to match its largest possible variant. By placing rarely encountered large variants behind pointers (boxing), the inline size of the standard enum dropped significantly.
• Storing raw wire-format bytes: Engineers converted record storage into length-prefixed raw wire-format byte buffers. This prevented short 4-byte A records from occupying the 144-byte structure reserved for rare, oversized records such as NAPTR^[1].

Fleet Rollout and Measurable Performance Gains

According to technical performance metrics compiled by MLQ.ai, the rollout spanned from May 18 through July 6, 2026, across Cloudflare's global data center fleet. Rather than suffering latency penalties from added indirection, the service saw substantial speed improvements due to improved CPU cache locality and fewer heap allocations.

Engineering Trade-Offs and Next Steps

While the architectural overhaul delivered massive resource gains, such deep memory compression introduces subtle engineering trade-offs. Rebuilding domain names and decoding raw wire format bytes at read time trades minor CPU decoding cycles for memory density. In Big Pineapple's production environment, the reduction in memory allocations and improved cache locality comfortably outweighed the added decoding cost^[2].

As reported by igor'sLAB and Cloudflare's technical update, the company intends to channel this newly liberated memory pool directly back into larger DNS cache capacities. Expanding local cache capacity in regional points of presence will elevate cache hit rates, cut lookup times for end users, and decrease repetitive upstream queries sent to authoritative DNS nameservers.