diff --git a/src/lib/auth/__tests__/acl.test.ts b/src/lib/auth/__tests__/acl.test.ts
new file mode 100644
index 00000000..cbc61519
--- /dev/null
+++ b/src/lib/auth/__tests__/acl.test.ts
@@ -0,0 +1,175 @@
+import { describe, expect, it, beforeEach } from 'vitest';
+import {
+  hasPermission,
+  hasAnyPermission,
+  hasAllPermissions,
+  isAtLeast,
+  isAtLeastRole,
+  clearAclCaches,
+  ROLES_PERMISSIONS,
+} from '../acl';
+import { UserRole, Permission } from '@/types/api';
+
+describe('ACL caching', () => {
+  beforeEach(() => {
+    clearAclCaches();
+  });
+
+  describe('hasPermission', () => {
+    it('returns true for admin with any permission', () => {
+      const user = { role: UserRole.ADMIN };
+      expect(hasPermission(user, Permission.COURSE_VIEW)).toBe(true);
+      expect(hasPermission(user, Permission.COURSE_CREATE)).toBe(true);
+      expect(hasPermission(user, Permission.ANALYTICS_VIEW)).toBe(true);
+    });
+
+    it('returns true for instructor with allowed permissions', () => {
+      const user = { role: UserRole.INSTRUCTOR };
+      expect(hasPermission(user, Permission.COURSE_VIEW)).toBe(true);
+      expect(hasPermission(user, Permission.COURSE_CREATE)).toBe(true);
+      expect(hasPermission(user, Permission.CONTENT_UPLOAD)).toBe(true);
+    });
+
+    it('returns false for instructor with admin-only permissions', () => {
+      const user = { role: UserRole.INSTRUCTOR };
+      expect(hasPermission(user, Permission.ANALYTICS_VIEW)).toBe(false);
+      expect(hasPermission(user, Permission.USER_MANAGE)).toBe(false);
+    });
+
+    it('returns true for student with allowed permissions', () => {
+      const user = { role: UserRole.STUDENT };
+      expect(hasPermission(user, Permission.COURSE_VIEW)).toBe(true);
+      expect(hasPermission(user, Permission.COURSE_DOWNLOAD)).toBe(true);
+      expect(hasPermission(user, Permission.CONTENT_ACCESS)).toBe(true);
+    });
+
+    it('returns false for student with instructor permissions', () => {
+      const user = { role: UserRole.STUDENT };
+      expect(hasPermission(user, Permission.COURSE_CREATE)).toBe(false);
+      expect(hasPermission(user, Permission.COURSE_EDIT)).toBe(false);
+    });
+
+    it('returns true for guest with course view permission', () => {
+      const user = { role: UserRole.GUEST };
+      expect(hasPermission(user, Permission.COURSE_VIEW)).toBe(true);
+    });
+
+    it('returns false for guest with other permissions', () => {
+      const user = { role: UserRole.GUEST };
+      expect(hasPermission(user, Permission.COURSE_CREATE)).toBe(false);
+      expect(hasPermission(user, Permission.COURSE_DOWNLOAD)).toBe(false);
+    });
+
+    it('returns false for null or undefined user', () => {
+      expect(hasPermission(null, Permission.COURSE_VIEW)).toBe(false);
+      expect(hasPermission(undefined, Permission.COURSE_VIEW)).toBe(false);
+    });
+
+    it('caches results for same role and permission', () => {
+      const user = { role: UserRole.STUDENT };
+      const result1 = hasPermission(user, Permission.COURSE_VIEW);
+      const result2 = hasPermission(user, Permission.COURSE_VIEW);
+      expect(result1).toBe(result2);
+    });
+  });
+
+  describe('hasAnyPermission', () => {
+    it('returns true if user has any of the permissions', () => {
+      const user = { role: UserRole.STUDENT };
+      expect(hasAnyPermission(user, [Permission.COURSE_VIEW, Permission.COURSE_CREATE])).toBe(true);
+      expect(hasAnyPermission(user, [Permission.COURSE_CREATE, Permission.COURSE_VIEW])).toBe(true);
+    });
+
+    it('returns false if user has none of the permissions', () => {
+      const user = { role: UserRole.GUEST };
+      expect(hasAnyPermission(user, [Permission.COURSE_CREATE, Permission.COURSE_EDIT])).toBe(false);
+    });
+
+    it('returns false for null or undefined user', () => {
+      expect(hasAnyPermission(null, [Permission.COURSE_VIEW])).toBe(false);
+      expect(hasAnyPermission(undefined, [Permission.COURSE_VIEW])).toBe(false);
+    });
+  });
+
+  describe('hasAllPermissions', () => {
+    it('returns true if user has all permissions', () => {
+      const user = { role: UserRole.ADMIN };
+      expect(hasAllPermissions(user, [Permission.COURSE_VIEW, Permission.COURSE_CREATE])).toBe(true);
+    });
+
+    it('returns false if user is missing any permission', () => {
+      const user = { role: UserRole.STUDENT };
+      expect(hasAllPermissions(user, [Permission.COURSE_VIEW, Permission.COURSE_CREATE])).toBe(false);
+    });
+
+    it('returns false for null or undefined user', () => {
+      expect(hasAllPermissions(null, [Permission.COURSE_VIEW])).toBe(false);
+      expect(hasAllPermissions(undefined, [Permission.COURSE_VIEW])).toBe(false);
+    });
+  });
+
+  describe('isAtLeast', () => {
+    it('returns true for admin at any role', () => {
+      const user = { role: UserRole.ADMIN };
+      expect(isAtLeast(user, UserRole.ADMIN)).toBe(true);
+      expect(isAtLeast(user, UserRole.INSTRUCTOR)).toBe(true);
+      expect(isAtLeast(user, UserRole.STUDENT)).toBe(true);
+      expect(isAtLeast(user, UserRole.GUEST)).toBe(true);
+    });
+
+    it('returns true for instructor at instructor or lower', () => {
+      const user = { role: UserRole.INSTRUCTOR };
+      expect(isAtLeast(user, UserRole.INSTRUCTOR)).toBe(true);
+      expect(isAtLeast(user, UserRole.STUDENT)).toBe(true);
+      expect(isAtLeast(user, UserRole.GUEST)).toBe(true);
+    });
+
+    it('returns false for instructor at admin', () => {
+      const user = { role: UserRole.INSTRUCTOR };
+      expect(isAtLeast(user, UserRole.ADMIN)).toBe(false);
+    });
+
+    it('returns false for null or undefined user', () => {
+      expect(isAtLeast(null, UserRole.GUEST)).toBe(false);
+      expect(isAtLeast(undefined, UserRole.GUEST)).toBe(false);
+    });
+  });
+
+  describe('isAtLeastRole', () => {
+    it('returns true for admin at any role', () => {
+      expect(isAtLeastRole(UserRole.ADMIN, UserRole.ADMIN)).toBe(true);
+      expect(isAtLeastRole(UserRole.ADMIN, UserRole.INSTRUCTOR)).toBe(true);
+      expect(isAtLeastRole(UserRole.ADMIN, UserRole.STUDENT)).toBe(true);
+      expect(isAtLeastRole(UserRole.ADMIN, UserRole.GUEST)).toBe(true);
+    });
+
+    it('returns true for instructor at instructor or lower', () => {
+      expect(isAtLeastRole(UserRole.INSTRUCTOR, UserRole.INSTRUCTOR)).toBe(true);
+      expect(isAtLeastRole(UserRole.INSTRUCTOR, UserRole.STUDENT)).toBe(true);
+      expect(isAtLeastRole(UserRole.INSTRUCTOR, UserRole.GUEST)).toBe(true);
+    });
+
+    it('returns false for instructor at admin', () => {
+      expect(isAtLeastRole(UserRole.INSTRUCTOR, UserRole.ADMIN)).toBe(false);
+    });
+
+    it('returns false for null or undefined role', () => {
+      expect(isAtLeastRole(null, UserRole.GUEST)).toBe(false);
+      expect(isAtLeastRole(undefined, UserRole.GUEST)).toBe(false);
+    });
+  });
+
+  describe('clearAclCaches', () => {
+    it('clears all caches', () => {
+      const user = { role: UserRole.STUDENT };
+      hasPermission(user, Permission.COURSE_VIEW);
+      isAtLeastRole(UserRole.STUDENT, UserRole.GUEST);
+      
+      clearAclCaches();
+      
+      // Should still work correctly after clearing
+      expect(hasPermission(user, Permission.COURSE_VIEW)).toBe(true);
+      expect(isAtLeastRole(UserRole.STUDENT, UserRole.GUEST)).toBe(true);
+    });
+  });
+});
\ No newline at end of file
diff --git a/src/lib/auth/acl.ts b/src/lib/auth/acl.ts
index 3aea0576..a204574c 100644
--- a/src/lib/auth/acl.ts
+++ b/src/lib/auth/acl.ts
@@ -24,14 +24,30 @@ export const ROLES_PERMISSIONS: Record<UserRole, Permission[]> = {
   GUEST: [Permission.COURSE_VIEW],
 };
 
+// Cache for permission lookups to avoid repeated evaluation
+const permissionCache = new Map<string, boolean>();
+
+/**
+ * Generate a cache key for permission checks.
+ */
+function getPermissionCacheKey(role: UserRole, permission: Permission): string {
+  return `${role}:${permission}`;
+}
+
 /**
  * Check if a user (or any object that contains a role) has a specific permission.
  */
 export function hasPermission(user: RoleHolder | null | undefined, permission: Permission): boolean {
   if (!user) return false;
 
+  const cacheKey = getPermissionCacheKey(user.role, permission);
+  const cached = permissionCache.get(cacheKey);
+  if (cached !== undefined) return cached;
+
   const permissions = ROLES_PERMISSIONS[user.role] ?? [];
-  return permissions.includes(permission);
+  const result = permissions.includes(permission);
+  permissionCache.set(cacheKey, result);
+  return result;
 }
 
 /**
@@ -68,6 +84,16 @@ export function isAtLeast(user: RoleHolder | null | undefined, role: UserRole):
   return isAtLeastRole(user.role, role);
 }
 
+// Cache for role hierarchy lookups
+const roleHierarchyCache = new Map<string, boolean>();
+
+/**
+ * Generate a cache key for role hierarchy checks.
+ */
+function getRoleHierarchyCacheKey(userRole: UserRole, requiredRole: UserRole): string {
+  return `${userRole}:${requiredRole}`;
+}
+
 /**
  * Check if a role has at least the minimum required role.
  * Roles are hierarchical: ADMIN > INSTRUCTOR > STUDENT > GUEST
@@ -75,9 +101,23 @@ export function isAtLeast(user: RoleHolder | null | undefined, role: UserRole):
 export function isAtLeastRole(userRole: UserRole | null | undefined, role: UserRole): boolean {
   if (!userRole) return false;
 
+  const cacheKey = getRoleHierarchyCacheKey(userRole, role);
+  const cached = roleHierarchyCache.get(cacheKey);
+  if (cached !== undefined) return cached;
+
   const hierarchy = [UserRole.GUEST, UserRole.STUDENT, UserRole.INSTRUCTOR, UserRole.ADMIN];
   const userRoleIndex = hierarchy.indexOf(userRole);
   const requiredRoleIndex = hierarchy.indexOf(role);
 
-  return userRoleIndex >= requiredRoleIndex;
+  const result = userRoleIndex >= requiredRoleIndex;
+  roleHierarchyCache.set(cacheKey, result);
+  return result;
+}
+
+/**
+ * Clear all ACL caches. Useful for testing or when caches need to be reset.
+ */
+export function clearAclCaches(): void {
+  permissionCache.clear();
+  roleHierarchyCache.clear();
 }
\ No newline at end of file