diff --git a/share-api/src/Share/Postgres/Contributions/Queries.hs b/share-api/src/Share/Postgres/Contributions/Queries.hs
index 7d233aa7..91753c82 100644
--- a/share-api/src/Share/Postgres/Contributions/Queries.hs
+++ b/share-api/src/Share/Postgres/Contributions/Queries.hs
@@ -260,10 +260,10 @@ listContributionsByUserId callerUserId userId limit mayCursor mayStatusFilter ma
         contribution.author_id,
         (SELECT COUNT(*) FROM comments comment WHERE comment.contribution_id = contribution.id AND comment.deleted_at IS NULL) as num_comments
       FROM contributions AS contribution
-        JOIN projects AS project ON project.id = contribution.project_id
+        JOIN projects_by_user_permission(#{callerUserId}, #{ProjectView}) AS project
+          ON project.id = contribution.project_id
       WHERE
         contribution.author_id = #{userId}
-        AND user_has_project_permission(#{callerUserId}, project.id, #{ProjectView})
         AND (#{mayStatusFilter} IS NULL OR contribution.status = #{mayStatusFilter})
         AND ^{cursorFilter}
         AND ^{kindFilter}
diff --git a/share-api/src/Share/Postgres/Queries.hs b/share-api/src/Share/Postgres/Queries.hs
index d7fee185..eb461d66 100644
--- a/share-api/src/Share/Postgres/Queries.hs
+++ b/share-api/src/Share/Postgres/Queries.hs
@@ -156,22 +156,20 @@ searchProjects caller userIdFilter (Query query) psk limit = do
       PG.queryListRows @(Project PG.:. PG.Only UserHandle)
         [PG.sql|
         SELECT p.id, p.owner_user_id, p.slug, p.summary, p.tags, p.private, p.created_at, p.updated_at, owner.handle
-          FROM projects p
+          FROM projects_by_user_permission(#{caller}, #{ProjectView}) p
             JOIN users owner ON p.owner_user_id = owner.id
           WHERE p.owner_user_id = #{userId}
-            AND user_has_project_permission(#{caller}, p.id, #{ProjectView})
-          ORDER BY p.created_at DESC
+          ORDER BY p.created_at DESC, p.slug ASC
           LIMIT #{limit}
           |]
     _ -> do
       PG.queryListRows
         [PG.sql|
       SELECT p.id, p.owner_user_id, p.slug, p.summary, p.tags, p.private, p.created_at, p.updated_at, owner.handle
-        FROM websearch_to_tsquery('english', #{query}) AS tokenquery, projects AS p
+        FROM websearch_to_tsquery('english', #{query}) AS tokenquery, projects_by_user_permission(#{caller}, #{ProjectView}) AS p
           JOIN users AS owner ON p.owner_user_id = owner.id
         WHERE (tokenquery @@ p.project_text_document OR p.slug ILIKE ('%' || like_escape(#{query}) || '%'))
         AND (#{userIdFilter} IS NULL OR p.owner_user_id = #{userIdFilter})
-        AND user_has_project_permission(#{caller}, p.id, #{ProjectView})
         ^{pskFilter}
         ORDER BY
           p.slug = #{query} DESC,
@@ -275,11 +273,10 @@ listProjectsByUserWithMetadata callerUserId projectOwnerUserId = do
           owner.handle,
           owner.name,
           EXISTS (SELECT FROM org_members WHERE org_members.organization_user_id = owner.id) AS is_org
-        FROM projects p
+        FROM projects_by_user_permission(#{callerUserId}, #{ProjectView}) AS p
           JOIN users owner ON owner.id = p.owner_user_id
         WHERE p.owner_user_id = #{projectOwnerUserId}
-          AND user_has_project_permission(#{callerUserId}, p.id, #{ProjectView})
-        ORDER BY p.created_at DESC
+        ORDER BY p.created_at DESC, p.slug ASC
       |]
   where
     unpackRows :: [Project PG.:. FavData PG.:. ProjectOwner] -> [(Project, FavData, ProjectOwner)]
@@ -878,12 +875,11 @@ listContributorBranchesOfUserAccessibleToCaller contributorUserId mayCallerUserI
               project_owner.name,
               EXISTS (SELECT FROM org_members WHERE org_members.organization_user_id = project.owner_user_id)
             FROM project_branches b
-            JOIN projects project ON project.id = b.project_id
+            JOIN projects_by_user_permission(#{mayCallerUserId}, #{ProjectView}) AS project ON project.id = b.project_id
             JOIN users AS project_owner ON project_owner.id = project.owner_user_id
             WHERE
               b.deleted_at IS NULL
               AND b.contributor_id = #{contributorUserId}
-              AND user_has_project_permission(#{mayCallerUserId}, b.project_id, #{ProjectView})
               |],
                 branchNameFilter,
                 cursorFilter,
diff --git a/share-api/src/Share/Postgres/Search/DefinitionSearch/Queries.hs b/share-api/src/Share/Postgres/Search/DefinitionSearch/Queries.hs
index 682a445a..18ef87ab 100644
--- a/share-api/src/Share/Postgres/Search/DefinitionSearch/Queries.hs
+++ b/share-api/src/Share/Postgres/Search/DefinitionSearch/Queries.hs
@@ -401,13 +401,13 @@ globalDefNameCompletionSearch mayCaller mayUserFilter (Query query) limit = do
     [sql|
     WITH results(name, tag) AS (
       SELECT DISTINCT doc.name, doc.tag FROM global_definition_search_docs doc
-        JOIN projects p ON p.id = doc.project_id
+        JOIN projects_by_user_permission(#{mayCaller}, #{ProjectView}) p
+          ON p.id = doc.project_id
         WHERE
           -- Find names which contain the query
           doc.name ILIKE ('%.' || like_escape(#{query}) || '%')
 
-        AND user_has_project_permission(#{mayCaller}, p.id, #{ProjectView})
-          ^{filters}
+        ^{filters}
       ) SELECT r.name, r.tag FROM results r
         -- Docs and tests to the bottom, then
         -- prefer matches where the original query appears (case-matched),
@@ -501,11 +501,11 @@ globalDefinitionTokenSearch mayCaller mayUserFilter limit searchTokens preferred
     queryListRows @(ProjectId, ReleaseId, Name, Hasql.Jsonb)
       [sql|
       SELECT doc.project_id, doc.release_id, doc.name, doc.metadata FROM global_definition_search_docs doc
-        JOIN projects p ON p.id = doc.project_id
+        JOIN projects_by_user_permission(#{mayCaller}, #{ProjectView}) p
+          ON p.id = doc.project_id
         WHERE
           -- match on search tokens using GIN index.
           tsquery(#{tsQueryText}) @@ doc.search_tokens
-        AND user_has_project_permission(#{mayCaller}, p.id, #{ProjectView})
         AND (#{preferredArity} IS NULL OR doc.arity >= #{preferredArity})
           ^{filters}
           ^{namesFilter}
@@ -619,11 +619,10 @@ globalDefinitionNameSearch mayCaller mayUserFilter limit (Query query) = do
     queryListRows @(ProjectId, ReleaseId, Name, Hasql.Jsonb)
       [sql|
       SELECT doc.project_id, doc.release_id, doc.name, doc.metadata FROM global_definition_search_docs doc
-        JOIN projects p ON p.id = doc.project_id
+        JOIN projects_by_user_permission(#{mayCaller}, #{ProjectView}) p ON p.id = doc.project_id
         WHERE
           -- We may wish to adjust the similarity threshold before the query.
           #{query} <% doc.name
-        AND user_has_project_permission(#{mayCaller}, p.id, #{ProjectView})
           ^{filters}
         -- Score matches by:
         -- - projects in the catalog
diff --git a/share-api/src/Share/Postgres/Tickets/Queries.hs b/share-api/src/Share/Postgres/Tickets/Queries.hs
index 76e26e3e..fa9b5e76 100644
--- a/share-api/src/Share/Postgres/Tickets/Queries.hs
+++ b/share-api/src/Share/Postgres/Tickets/Queries.hs
@@ -251,10 +251,9 @@ listTicketsByUserId callerUserId userId limit mayCursor mayStatusFilter = do
         ticket.author_id,
         (SELECT COUNT(*) FROM comments comment WHERE comment.ticket_id = ticket.id AND comment.deleted_at IS NULL) as num_comments
       FROM tickets AS ticket
-        JOIN projects AS project ON project.id = ticket.project_id
+        JOIN projects_by_user_permission(#{callerUserId}, #{ProjectView}) AS project ON project.id = ticket.project_id
       WHERE
         ticket.author_id = #{userId}
-        AND user_has_project_permission(#{callerUserId}, project.id, #{ProjectView})
         AND (#{mayStatusFilter} IS NULL OR ticket.status = #{mayStatusFilter}::ticket_status)
         AND ^{cursorFilter}
       ORDER BY ticket.updated_at DESC, ticket.id DESC
diff --git a/sql/2025-12-15_faster-project-by-permissions.sql b/sql/2025-12-15_faster-project-by-permissions.sql
new file mode 100644
index 00000000..7110df16
--- /dev/null
+++ b/sql/2025-12-15_faster-project-by-permissions.sql
@@ -0,0 +1,45 @@
+-- The previous user_has_project_permission function is called on _every_ project when doing global omnisearch,
+-- which is too slow.
+
+-- Create a view which serves as join table for finding projects for which the user has a given permission, it's much faster
+-- than running a permission check for every private project when we need to discover the list of all projects a user
+-- has access to.
+-- 
+-- This special-cases the 'project:view' permission to be even faster, it's the most common case.
+CREATE FUNCTION projects_by_user_permission(arg_user_id UUID, arg_permission permission)
+-- Returns a subset of the projects table
+RETURNS SETOF projects AS $$
+  -- Get all public projects and projects owned by the user,
+  -- as well as all public projects.
+  SELECT p.*
+    FROM projects p
+    WHERE p.owner_user_id = arg_user_id 
+      OR (arg_permission = 'project:view' AND NOT p.private)
+UNION
+  SELECT
+    p.*
+    FROM org_members om
+      JOIN projects p 
+        ON om.organization_user_id = p.owner_user_id
+      JOIN roles r ON om.role_id = r.id
+      WHERE om.member_user_id = arg_user_id
+        AND arg_permission = ANY(r.permissions)
+        -- All public projects are already included above if the permission is 'project:view'
+        AND (p.private OR arg_permission <> 'project:view')
+  UNION
+  -- Include projects the user is a direct maintainer of
+  SELECT
+    p.*
+    FROM users u
+      JOIN role_memberships rm ON u.subject_id = rm.subject_id
+      JOIN roles r ON rm.role_id = r.id
+      JOIN projects p ON rm.resource_id = p.resource_id
+      WHERE u.id = arg_user_id
+        AND arg_permission = ANY(r.permissions)
+        -- All public projects are already included above if the permission is 'project:view'
+        AND (p.private OR arg_permission <> 'project:view')
+$$ LANGUAGE sql STABLE PARALLEL SAFE;
+
+-- A better index for this query.
+CREATE INDEX idx_projects_by_owner_and_privacy
+  ON projects (private, owner_user_id);
diff --git a/transcripts/share-apis/project-maintainers/out/read-maintainer-project-list-after.json b/transcripts/share-apis/project-maintainers/out/read-maintainer-project-list-after.json
index d64ee06c..0a9d2604 100644
--- a/transcripts/share-apis/project-maintainers/out/read-maintainer-project-list-after.json
+++ b/transcripts/share-apis/project-maintainers/out/read-maintainer-project-list-after.json
@@ -3,32 +3,32 @@
     {
       "createdAt": "<TIMESTAMP>",
       "isFaved": false,
-      "numFavs": 1,
+      "numFavs": 0,
       "owner": {
         "handle": "@test",
         "name": null,
         "type": "user"
       },
-      "slug": "publictestproject",
-      "summary": "test project summary",
+      "slug": "privatetestproject",
+      "summary": "private summary",
       "tags": [],
       "updatedAt": "<TIMESTAMP>",
-      "visibility": "public"
+      "visibility": "private"
     },
     {
       "createdAt": "<TIMESTAMP>",
       "isFaved": false,
-      "numFavs": 0,
+      "numFavs": 1,
       "owner": {
         "handle": "@test",
         "name": null,
         "type": "user"
       },
-      "slug": "privatetestproject",
-      "summary": "private summary",
+      "slug": "publictestproject",
+      "summary": "test project summary",
       "tags": [],
       "updatedAt": "<TIMESTAMP>",
-      "visibility": "private"
+      "visibility": "public"
     }
   ],
   "status": [