A TimestampSigner value is an HMAC over 'payload:timestamp', so a plain
Signer's HMAC check accepts it and the embedded timestamp then reached the
JSON decoder, raising JSONDecodeError (not BadSignature) and surfacing as a
500. That broke every stored visual-match thumbnail URL minted before the
stable scheme, so the J-ID match tiles never loaded on prod.
Detect the legacy shape by its extra separator and verify it with
TimestampSigner; malformed input returns None instead of raising.
Signed media URLs embedded the current second (TimestampSigner), so every
API response re-minted every raw/thumbnail/staged URL and the browser
re-downloaded each file on every poll or navigation. Responses also carried
no cache headers at all.
- sign with a plain Signer plus a bucket-quantized exp (7d TTL, 24h bucket),
so a URL is byte-identical across responses and rotates once a day; legacy
TimestampSigner URLs stay accepted for one release
- add a v=<md5> version parameter to library media URLs so replacing a file
under the same J-ID (the optimize flow) busts caches exactly when needed
- serve_file now sends ETag/Last-Modified and a private Cache-Control and
answers conditional requests with 304; library media gets max-age 6d +
immutable, staged/similarity files 1h
- build cached 480px JPEG thumbnails for images (Pillow, keyed by MD5 under
MEDIA_ROOT/thumbs) instead of serving full-size originals through the
thumbnail endpoint; the library grid uses thumbnail_url for images too
JakeBreath