Range-Requests As A Remote Binary-Search Primitive Over Large Static Files

Issue 58 Edition 2026-02-27 5 min read

General

Sources: 1 • Confidence: High • Updated: 2026-04-12 10:09

Key takeaways

The demo accepts either a single character or a hexadecimal Unicode codepoint input and displays the intermediate steps of the binary search through the large file.
HTTP Range-request techniques are not compatible with HTTP compression because compression breaks byte-offset calculations.
The tool was deployed to tools.simonwillison.net and queries a CORS-enabled 76.6MB file hosted in S3 and fronted by Cloudflare using Range requests.
Claude was used to generate a specification and Claude Code for web was used to turn it into working code via an asynchronous research workflow.
A prototype was built from a phone as an experiment in using HTTP Range requests.

The demo accepts either a single character or a hexadecimal Unicode codepoint input and displays the intermediate steps of the binary search through the large file.
A prototype was built from a phone as an experiment in using HTTP Range requests.
The prototype searches a large file by performing a binary search implemented via HTTP Range requests.
A proposed use case for the approach is looking up Unicode codepoint metadata by searching through many megabytes of data.
This Range-request binary-search approach requires data that is naturally sorted to be useful.

HTTP Range-request techniques are not compatible with HTTP compression because compression breaks byte-offset calculations.

The tool was deployed to tools.simonwillison.net and queries a CORS-enabled 76.6MB file hosted in S3 and fronted by Cloudflare using Range requests.

Claude was used to generate a specification and Claude Code for web was used to turn it into working code via an asynchronous research workflow.

What are the observed latency and request-count characteristics for typical lookups (e.g., number of Range requests per query, median/worst-case time)?
What is the egress and CDN cost profile of repeated interactive queries against the 76.6MB file (including cache hit rates and byte-transfer per query)?
How is HTTP compression practically handled end-to-end (origin, CDN, browser) to guarantee stable byte offsets for Range responses?
What file format and record layout is used to make binary search feasible (e.g., fixed-width records vs variable-length lines), and what are the failure modes when records are variable-length?
What cross-browser and CDN interoperability issues were encountered (Range semantics, CORS edge cases, caching behavior), if any?

Range requests enable browser-side querying of large static files on commodity S3 plus CDN setups, suggesting incremental demand for reliable partial-content delivery, CORS, and cache behavior in CDNs and object storage when developers adopt this pattern.
The no-compression constraint highlights a correctness tradeoff that could drive demand for CDN and origin controls that guarantee stable byte offsets, potentially influencing how teams configure delivery for data files used with range-based lookup.
AI-assisted prototyping from spec to working code indicates tooling workflows where LLMs and coding agents accelerate experimentation, potentially increasing the pace of small web-deployed demos and internal tools that rely on CDN-hosted assets.

Broader publication of benchmarks showing acceptable latency and request counts for typical lookups, plus evidence of repeated interactive usage without prohibitive egress or CDN costs.
Clear, repeatable deployment guidance demonstrating how to disable or avoid compression end to end while preserving CORS, caching, and correct Range semantics across common CDNs and browsers.
Reports of additional tools or deployments adopting the same architecture pattern of browser-accessible range reads against a single large sorted file hosted on object storage and fronted by a CDN.

Observed lookup performance is poor due to high request counts, high median latency, or worst-case tail latency that makes interactive use impractical in browsers.
Egress and CDN billing for interactive queries is uneconomic because cache hit rates are low or byte transfer per query is high, limiting practical deployments.
Interoperability issues with Range handling, caching, CORS, or inadvertent compression across browsers or CDNs cause incorrect results or fragile deployments.