feat: implement LRU TTL refresh for S3 cache on Open#173
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alecthomas
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Mar 12, 2026
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| // refreshExpiration updates the Expires-At metadata on an S3 object using | ||
| // server-side copy-to-self with metadata replacement. This avoids re-uploading |
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going to spin it off into an async routine so it doesnt block. it will also only trigger when we're 50% of the way or more towards the TTL
Like the disk cache, S3 now resets the expiration time on each Open (read) using server-side copy-to-self with metadata replacement. This prevents frequently accessed snapshots from expiring while periodic snapshot jobs handle content freshness. Co-authored-by: Amp <amp@ampcode.com> Amp-Thread-ID: https://ampcode.com/threads/T-019cda52-ee36-738c-86cd-1fd410c47d7f
Amp-Thread-ID: https://ampcode.com/threads/T-019ce3ae-e3e4-72ff-b9ac-b71024e40dd3 Co-authored-by: Amp <amp@ampcode.com>
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Problem
S3 cache entries expire based on creation time (fixed TTL). Frequently accessed snapshots expire after 72h regardless of usage, causing cold cache misses after pod restarts when no periodic jobs are running to refresh them.
Solution
Like the disk cache, S3 now resets the expiration time on each
Openusing a server-side copy-to-self with metadata replacement (CopyObjectwithReplaceMetadata). No data is re-uploaded — only theExpires-Atuser metadata is updated.Content freshness is still handled by periodic
generateAndUploadSnapshotjobs (every 1h) which overwrite the S3 entry with a fresh snapshot from the latest git state.