nix/doc/manual/rl-next/s3-curl-implementation.md

synopsis	prs	issues
Improved S3 binary cache support via HTTP	13823 14026 14120 14131 14135 14144 14170 14190 14198 14206 14209 14222 14223 13752	13084 12671 11748 12403

S3 binary cache operations now happen via HTTP, leveraging libcurl's native AWS SigV4 authentication instead of the AWS C++ SDK, providing significant improvements:

• Reduced memory usage: Eliminates memory buffering issues that caused segfaults with large files
• Fixed upload reliability: Resolves AWS SDK chunking errors (InvalidChunkSizeError)
• Lighter dependencies: Uses lightweight aws-crt-cpp instead of full aws-cpp-sdk, reducing build complexity

The new implementation requires curl >= 7.75.0 and aws-crt-cpp for credential management.

All existing S3 URL formats and parameters remain supported, with the notable exception of multi-part uploads, which are no longer supported.

Note that this change also means Nix now supports S3 binary cache stores even if build without aws-crt-cpp, but only for public buckets which do not require auth.