Feat: Replace UUID image identifiers with 8-character base62 short IDs

Short IDs become the canonical identifier in URLs (/i/:short_id),
MinIO/R2 storage keys, and all API responses. Hash-based deduplication
is preserved. Includes two-phase Alembic migration (003 adds nullable
column, 004 enforces NOT NULL) with a backfill script to copy storage
objects and populate short_id for existing images.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/app/auth/rate_limiter.py

@@ -92,9 +92,7 @@ class LoginRateLimiter:
             rec.failures += 1
             if rec.failures >= self._max:
                 rec.blocked_until = now + self._cooldown
-                logger.warning(
-                    "Login blocked for %s after %d failures", ip, rec.failures
-                )
+                logger.warning("Login blocked for %s after %d failures", ip, rec.failures)
 
     def record_success(self, ip: str) -> None:
         with self._lock:

api/app/models.py

@@ -22,6 +22,7 @@ class Image(Base):
     size_bytes: Mapped[int] = mapped_column(BigInteger, nullable=False)
     width: Mapped[int] = mapped_column(Integer, nullable=False)
     height: Mapped[int] = mapped_column(Integer, nullable=False)
+    short_id: Mapped[str | None] = mapped_column(String(8), unique=True, nullable=True, index=True)
     storage_key: Mapped[str] = mapped_column(String(64), nullable=False)
     thumbnail_key: Mapped[str | None] = mapped_column(String(70), nullable=True, default=None)
     created_at: Mapped[datetime] = mapped_column(

api/app/repositories/image_repo.py

@@ -27,6 +27,14 @@ class ImageRepository:
         )
         return result.scalar_one_or_none()
 
+    async def get_by_short_id(self, short_id: str) -> Image | None:
+        result = await self._session.execute(
+            select(Image)
+            .where(Image.short_id == short_id)
+            .options(selectinload(Image.image_tags).selectinload(ImageTag.tag))
+        )
+        return result.scalar_one_or_none()
+
     async def create(
         self,
         *,
@@ -37,6 +45,7 @@ class ImageRepository:
         width: int,
         height: int,
         storage_key: str,
+        short_id: str,
         thumbnail_key: str | None = None,
     ) -> Image:
         image = Image(
@@ -47,6 +56,7 @@ class ImageRepository:
             width=width,
             height=height,
             storage_key=storage_key,
+            short_id=short_id,
             thumbnail_key=thumbnail_key,
         )
         self._session.add(image)

api/app/repositories/tag_repo.py

@@ -48,9 +48,7 @@ class TagRepository:
         for name in tag_names:
             tag = await self.upsert_by_name(name)
             existing = await self._session.execute(
-                select(ImageTag).where(
-                    ImageTag.image_id == image.id, ImageTag.tag_id == tag.id
-                )
+                select(ImageTag).where(ImageTag.image_id == image.id, ImageTag.tag_id == tag.id)
             )
             if existing.scalar_one_or_none() is None:
                 self._session.add(ImageTag(image_id=image.id, tag_id=tag.id))
@@ -102,7 +100,6 @@ class TagRepository:
         rows = await self._session.execute(paginated)
 
         items = [
-            {"id": str(tag.id), "name": tag.name, "image_count": count}
-            for tag, count in rows.all()
+            {"id": str(tag.id), "name": tag.name, "image_count": count} for tag, count in rows.all()
         ]
         return items, total

api/app/routers/images.py

@@ -1,7 +1,7 @@
 import asyncio
 import logging
+import re
 import struct
-import uuid
 from typing import Any
 
 from fastapi import APIRouter, Depends, File, Form, HTTPException, Response, UploadFile
@@ -15,7 +15,7 @@ from app.repositories.image_repo import ImageRepository
 from app.repositories.tag_repo import TagRepository
 from app.storage.backend import StorageBackend
 from app.thumbnail import generate_thumbnail
-from app.utils import compute_sha256
+from app.utils import compute_sha256, generate_short_id
 from app.validation import FileSizeError, MimeTypeError, validate_file_size, validate_mime_type
 
 logger = logging.getLogger(__name__)
@@ -23,22 +23,35 @@ logger = logging.getLogger(__name__)
 router = APIRouter(tags=["images"])
 
 
+_SHORT_ID_RE = re.compile(r"^[a-zA-Z0-9]{8}$")
+
+
 def _error(detail: str, code: str, status: int):
     raise HTTPException(status_code=status, detail={"detail": detail, "code": code})
 
 
+def _validate_short_id(short_id: str) -> str:
+    if not _SHORT_ID_RE.match(short_id):
+        raise HTTPException(
+            status_code=422,
+            detail={"detail": "Invalid image ID", "code": "invalid_short_id"},
+        )
+    return short_id
+
+
 def _image_to_dict(
     image: Image, *, cdn_base: str | None = None, duplicate: bool | None = None
 ) -> dict[str, Any]:
     _base = cdn_base.strip().rstrip("/") if cdn_base else None
-    file_url = f"{_base}/{image.storage_key}" if _base else f"/api/v1/images/{image.id}/file"
+    file_url = f"{_base}/{image.storage_key}" if _base else f"/api/v1/i/{image.short_id}/file"
     thumbnail_url = (
-        (f"{_base}/{image.thumbnail_key}" if _base else f"/api/v1/images/{image.id}/thumbnail")
+        (f"{_base}/{image.thumbnail_key}" if _base else f"/api/v1/i/{image.short_id}/thumbnail")
         if image.thumbnail_key
         else None
     )
     data: dict[str, Any] = {
         "id": str(image.id),
+        "short_id": image.short_id,
         "hash": image.hash,
         "filename": image.filename,
         "mime_type": image.mime_type,
@@ -169,29 +182,49 @@ async def upload_image(
             )
 
     width, height = _read_image_dimensions(data, mime_type)
-    await storage.put(hash_hex, data, mime_type)
 
-    thumbnail_key: str | None = None
-    try:
-        thumb_bytes = await asyncio.to_thread(generate_thumbnail, data, mime_type)
-        await storage.put(f"{hash_hex}-thumb", thumb_bytes, "image/webp")
-        thumbnail_key = f"{hash_hex}-thumb"
-    except Exception:
-        logger.warning(
-            "Thumbnail generation failed for %s; upload will proceed without thumbnail", hash_hex
+    from sqlalchemy.exc import IntegrityError
+
+    for _ in range(10):
+        short_id = generate_short_id()
+        await storage.put(short_id, data, mime_type)
+
+        thumbnail_key: str | None = None
+        try:
+            thumb_bytes = await asyncio.to_thread(generate_thumbnail, data, mime_type)
+            await storage.put(f"{short_id}-thumb", thumb_bytes, "image/webp")
+            thumbnail_key = f"{short_id}-thumb"
+        except Exception:
+            logger.warning(
+                "Thumbnail generation failed for %s; proceeding without thumbnail", short_id
+            )
+
+        try:
+            image = await image_repo.create(
+                hash_hex=hash_hex,
+                filename=file.filename or "upload",
+                mime_type=mime_type,
+                size_bytes=len(data),
+                width=width,
+                height=height,
+                storage_key=short_id,
+                short_id=short_id,
+                thumbnail_key=thumbnail_key,
+            )
+            break
+        except IntegrityError:
+            await db.rollback()
+            await storage.delete(short_id)
+            if thumbnail_key:
+                await storage.delete(thumbnail_key)
+            thumbnail_key = None
+            continue
+    else:
+        raise HTTPException(
+            status_code=500,
+            detail={"detail": "Failed to assign unique ID", "code": "id_collision"},
         )
 
-    image = await image_repo.create(
-        hash_hex=hash_hex,
-        filename=file.filename or "upload",
-        mime_type=mime_type,
-        size_bytes=len(data),
-        width=width,
-        height=height,
-        storage_key=hash_hex,
-        thumbnail_key=thumbnail_key,
-    )
-
     if tag_names:
         tag_repo = TagRepository(db)
         await tag_repo.attach_tags(image, tag_names)
@@ -221,15 +254,16 @@ async def list_images(
     }
 
 
-@router.get("/images/{image_id}")
+@router.get("/i/{short_id}")
 async def get_image(
-    image_id: uuid.UUID,
+    short_id: str,
     db: AsyncSession = Depends(get_db),
     settings=Depends(get_settings),
 ):
+    _validate_short_id(short_id)
     _cdn_base = settings.s3_public_base_url
     image_repo = ImageRepository(db)
-    image = await image_repo.get_by_id(image_id)
+    image = await image_repo.get_by_short_id(short_id)
     if not image:
         raise HTTPException(
             status_code=404,
@@ -238,14 +272,15 @@ async def get_image(
     return _image_to_dict(image, cdn_base=_cdn_base)
 
 
-@router.get("/images/{image_id}/file")
+@router.get("/i/{short_id}/file")
 async def serve_image_file(
-    image_id: uuid.UUID,
+    short_id: str,
     db: AsyncSession = Depends(get_db),
     storage: StorageBackend = Depends(get_storage),
 ):
+    _validate_short_id(short_id)
     image_repo = ImageRepository(db)
-    image = await image_repo.get_by_id(image_id)
+    image = await image_repo.get_by_short_id(short_id)
     if not image:
         raise HTTPException(
             status_code=404,
@@ -268,14 +303,15 @@ async def serve_image_file(
     )
 
 
-@router.get("/images/{image_id}/thumbnail")
+@router.get("/i/{short_id}/thumbnail")
 async def serve_image_thumbnail(
-    image_id: uuid.UUID,
+    short_id: str,
     db: AsyncSession = Depends(get_db),
     storage: StorageBackend = Depends(get_storage),
 ):
+    _validate_short_id(short_id)
     image_repo = ImageRepository(db)
-    image = await image_repo.get_by_id(image_id)
+    image = await image_repo.get_by_short_id(short_id)
     if not image:
         raise HTTPException(
             status_code=404,
@@ -300,17 +336,18 @@ async def serve_image_thumbnail(
     )
 
 
-@router.patch("/images/{image_id}/tags")
+@router.patch("/i/{short_id}/tags")
 async def update_image_tags(
-    image_id: uuid.UUID,
+    short_id: str,
     body: dict,
     db: AsyncSession = Depends(get_db),
     _: Identity = Depends(require_auth),
     settings=Depends(get_settings),
 ):
+    _validate_short_id(short_id)
     _cdn_base = settings.s3_public_base_url
     image_repo = ImageRepository(db)
-    image = await image_repo.get_by_id(image_id)
+    image = await image_repo.get_by_short_id(short_id)
     if not image:
         raise HTTPException(
             status_code=404,
@@ -332,15 +369,16 @@ async def update_image_tags(
     return _image_to_dict(image, cdn_base=_cdn_base)
 
 
-@router.delete("/images/{image_id}", status_code=204)
+@router.delete("/i/{short_id}", status_code=204)
 async def delete_image(
-    image_id: uuid.UUID,
+    short_id: str,
     db: AsyncSession = Depends(get_db),
     storage: StorageBackend = Depends(get_storage),
     _: Identity = Depends(require_auth),
 ):
+    _validate_short_id(short_id)
     image_repo = ImageRepository(db)
-    image = await image_repo.get_by_id(image_id)
+    image = await image_repo.get_by_short_id(short_id)
     if not image:
         raise HTTPException(
             status_code=404,

api/app/utils.py

@@ -1,5 +1,13 @@
 import hashlib
+import secrets
+import string
+
+BASE62 = string.ascii_letters + string.digits
 
 
 def compute_sha256(data: bytes) -> str:
     return hashlib.sha256(data).hexdigest()
+
+
+def generate_short_id(length: int = 8) -> str:
+    return "".join(secrets.choice(BASE62) for _ in range(length))