diff --git a/src/lib.rs b/src/lib.rs
index d0471986..b2fc17a4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -105,7 +105,10 @@ async fn ensure_details<R: FullRepo, S: Store + 'static>(
     store: &S,
     alias: &Alias,
 ) -> Result<Details, Error> {
-    let identifier = repo.identifier_from_alias::<S::Identifier>(alias).await?;
+    let Some(identifier) = repo.identifier_from_alias::<S::Identifier>(alias).await? else {
+        return Err(UploadError::MissingAlias.into());
+    };
+
     let details = repo.details(&identifier).await?;
 
     if let Some(details) = details {
@@ -573,7 +576,13 @@ async fn process_details<R: FullRepo, S: Store>(
 ) -> Result<HttpResponse, Error> {
     let (_, alias, thumbnail_path, _) = prepare_process(query, ext.as_str())?;
 
-    let hash = repo.hash(&alias).await?;
+    let Some(hash) = repo.hash(&alias).await? else {
+        // Invalid alias
+        return Ok(HttpResponse::NotFound().json(&serde_json::json!({
+            "msg": "No images associated with provided alias",
+        })));
+    };
+
     let identifier = repo
         .variant_identifier::<S::Identifier>(hash, thumbnail_path.to_string_lossy().to_string())
         .await?
@@ -598,7 +607,11 @@ async fn process<R: FullRepo, S: Store + 'static>(
     let (format, alias, thumbnail_path, thumbnail_args) = prepare_process(query, ext.as_str())?;
 
     let path_string = thumbnail_path.to_string_lossy().to_string();
-    let hash = repo.hash(&alias).await?;
+    let Some(hash) = repo.hash(&alias).await? else {
+        // Invalid alias
+        // TODO: placeholder 404 image
+        return Ok(HttpResponse::NotFound().finish());
+    };
 
     let identifier_opt = repo
         .variant_identifier::<S::Identifier>(hash.clone(), path_string)
@@ -685,7 +698,11 @@ async fn process_head<R: FullRepo, S: Store + 'static>(
     let (format, alias, thumbnail_path, _) = prepare_process(query, ext.as_str())?;
 
     let path_string = thumbnail_path.to_string_lossy().to_string();
-    let hash = repo.hash(&alias).await?;
+    let Some(hash) = repo.hash(&alias).await? else {
+        // Invalid alias
+        return Ok(HttpResponse::NotFound().finish());
+    };
+
     let identifier_opt = repo
         .variant_identifier::<S::Identifier>(hash.clone(), path_string)
         .await?;
@@ -726,7 +743,11 @@ async fn process_backgrounded<R: FullRepo, S: Store>(
     let (target_format, source, process_path, process_args) = prepare_process(query, ext.as_str())?;
 
     let path_string = process_path.to_string_lossy().to_string();
-    let hash = repo.hash(&source).await?;
+    let Some(hash) = repo.hash(&source).await? else {
+        // Invalid alias
+        return Ok(HttpResponse::BadRequest().finish());
+    };
+
     let identifier_opt = repo
         .variant_identifier::<S::Identifier>(hash.clone(), path_string)
         .await?;
@@ -764,7 +785,11 @@ async fn serve<R: FullRepo, S: Store + 'static>(
 ) -> Result<HttpResponse, Error> {
     let alias = alias.into_inner();
 
-    let identifier = repo.identifier_from_alias::<S::Identifier>(&alias).await?;
+    let Some(identifier) = repo.identifier_from_alias::<S::Identifier>(&alias).await? else {
+        // Invalid alias
+        // TODO: placeholder 404 image
+        return Ok(HttpResponse::NotFound().finish());
+    };
 
     let details = ensure_details(&repo, &store, &alias).await?;
 
@@ -780,7 +805,10 @@ async fn serve_head<R: FullRepo, S: Store + 'static>(
 ) -> Result<HttpResponse, Error> {
     let alias = alias.into_inner();
 
-    let identifier = repo.identifier_from_alias::<S::Identifier>(&alias).await?;
+    let Some(identifier) = repo.identifier_from_alias::<S::Identifier>(&alias).await? else {
+        // Invalid alias
+        return Ok(HttpResponse::NotFound().finish());
+    };
 
     let details = ensure_details(&repo, &store, &alias).await?;
 
@@ -932,7 +960,11 @@ async fn purge<R: FullRepo>(
     let alias = query.into_inner().alias;
     let aliases = repo.aliases_from_alias(&alias).await?;
 
-    let hash = repo.hash(&alias).await?;
+    let Some(hash) = repo.hash(&alias).await? else {
+        return Ok(HttpResponse::BadRequest().json(&serde_json::json!({
+            "msg": "No images associated with provided alias",
+        })));
+    };
     queue::cleanup_hash(&repo, hash).await?;
 
     Ok(HttpResponse::Ok().json(&serde_json::json!({
@@ -961,7 +993,12 @@ async fn identifier<R: FullRepo, S: Store>(
     repo: web::Data<R>,
 ) -> Result<HttpResponse, Error> {
     let alias = query.into_inner().alias;
-    let identifier = repo.identifier_from_alias::<S::Identifier>(&alias).await?;
+    let Some(identifier) = repo.identifier_from_alias::<S::Identifier>(&alias).await? else {
+        // Invalid alias
+        return Ok(HttpResponse::NotFound().json(serde_json::json!({
+            "msg": "No identifiers associated with provided alias"
+        })));
+    };
 
     Ok(HttpResponse::Ok().json(&serde_json::json!({
         "msg": "ok",
diff --git a/src/queue/cleanup.rs b/src/queue/cleanup.rs
index 7beb5ff0..dd3c667c 100644
--- a/src/queue/cleanup.rs
+++ b/src/queue/cleanup.rs
@@ -127,9 +127,13 @@ where
         return Err(UploadError::InvalidToken.into());
     }
 
-    let hash = repo.hash(&alias).await?;
-
     AliasRepo::cleanup(repo, &alias).await?;
+
+    let Some(hash) = repo.hash(&alias).await? else {
+        // hash doesn't exist, nothing to do
+        return Ok(());
+    };
+
     repo.remove_alias(hash.clone(), &alias).await?;
 
     if repo.aliases(hash.clone()).await?.is_empty() {
diff --git a/src/queue/process.rs b/src/queue/process.rs
index 636129a3..e06952e7 100644
--- a/src/queue/process.rs
+++ b/src/queue/process.rs
@@ -125,7 +125,10 @@ async fn generate<R: FullRepo, S: Store + 'static>(
     process_path: PathBuf,
     process_args: Vec<String>,
 ) -> Result<(), Error> {
-    let hash = repo.hash(&source).await?;
+    let Some(hash) = repo.hash(&source).await? else {
+        // Nothing to do
+        return Ok(());
+    };
 
     let path_string = process_path.to_string_lossy().to_string();
     let identifier_opt = repo
diff --git a/src/repo.rs b/src/repo.rs
index 84e8fb86..a8ece2a1 100644
--- a/src/repo.rs
+++ b/src/repo.rs
@@ -86,14 +86,20 @@ pub(crate) trait FullRepo:
     async fn identifier_from_alias<I: Identifier + 'static>(
         &self,
         alias: &Alias,
-    ) -> Result<I, StoreError> {
-        let hash = self.hash(alias).await?;
-        self.identifier(hash).await
+    ) -> Result<Option<I>, StoreError> {
+        let Some(hash) = self.hash(alias).await? else {
+            return Ok(None);
+        };
+
+        self.identifier(hash).await.map(Some)
     }
 
     #[tracing::instrument(skip(self))]
     async fn aliases_from_alias(&self, alias: &Alias) -> Result<Vec<Alias>, RepoError> {
-        let hash = self.hash(alias).await?;
+        let Some(hash) = self.hash(alias).await? else {
+            return Ok(vec![]);
+        };
+
         self.aliases(hash).await
     }
 
@@ -102,7 +108,10 @@ pub(crate) trait FullRepo:
         &self,
         alias: &Alias,
     ) -> Result<Option<I>, StoreError> {
-        let hash = self.hash(alias).await?;
+        let Some(hash) = self.hash(alias).await? else {
+            return Ok(None);
+        };
+
         let identifier = self.identifier::<I>(hash.clone()).await?;
 
         match self.details(&identifier).await? {
@@ -411,7 +420,7 @@ pub(crate) trait AliasRepo: BaseRepo {
     async fn delete_token(&self, alias: &Alias) -> Result<DeleteToken, RepoError>;
 
     async fn relate_hash(&self, alias: &Alias, hash: Self::Bytes) -> Result<(), RepoError>;
-    async fn hash(&self, alias: &Alias) -> Result<Self::Bytes, RepoError>;
+    async fn hash(&self, alias: &Alias) -> Result<Option<Self::Bytes>, RepoError>;
 
     async fn cleanup(&self, alias: &Alias) -> Result<(), RepoError>;
 }
@@ -441,7 +450,7 @@ where
         T::relate_hash(self, alias, hash).await
     }
 
-    async fn hash(&self, alias: &Alias) -> Result<Self::Bytes, RepoError> {
+    async fn hash(&self, alias: &Alias) -> Result<Option<Self::Bytes>, RepoError> {
         T::hash(self, alias).await
     }
 
diff --git a/src/repo/sled.rs b/src/repo/sled.rs
index 04c06236..ab41230e 100644
--- a/src/repo/sled.rs
+++ b/src/repo/sled.rs
@@ -729,13 +729,12 @@ impl AliasRepo for SledRepo {
     }
 
     #[tracing::instrument(level = "trace", skip(self))]
-    async fn hash(&self, alias: &Alias) -> Result<Self::Bytes, RepoError> {
+    async fn hash(&self, alias: &Alias) -> Result<Option<Self::Bytes>, RepoError> {
         let key = alias.to_bytes();
 
         let opt = b!(self.alias_hashes, alias_hashes.get(key));
 
-        opt.ok_or(SledError::Missing("alias -> hash"))
-            .map_err(RepoError::from)
+        Ok(opt)
     }
 
     #[tracing::instrument(skip(self))]