diff --git a/PluralKit.API/Controllers/PKControllerBase.cs b/PluralKit.API/Controllers/PKControllerBase.cs
index 10f18c16..a3cec128 100644
--- a/PluralKit.API/Controllers/PKControllerBase.cs
+++ b/PluralKit.API/Controllers/PKControllerBase.cs
@@ -12,6 +12,9 @@ public class PKControllerBase: ControllerBase
     private readonly Regex _shortIdRegex = new("^[a-z]{5}$");
     private readonly Regex _snowflakeRegex = new("^[0-9]{17,19}$");
 
+    private List<PKMember>? _memberLookupCache { get; set; }
+    private List<PKGroup>? _groupLookupCache { get; set; }
+
     protected readonly ApiConfig _config;
     protected readonly IDatabase _db;
     protected readonly ModelRepository _repo;
@@ -47,26 +50,54 @@ public class PKControllerBase: ControllerBase
         return Task.FromResult<PKSystem?>(null);
     }
 
-    protected Task<PKMember?> ResolveMember(string memberRef)
+    protected async Task<PKMember?> ResolveMember(string memberRef, bool cache = false)
     {
+        if (cache)
+        {
+            if (_memberLookupCache == null)
+            {
+                HttpContext.Items.TryGetValue("SystemId", out var systemId);
+                if (systemId == null)
+                    throw new Exception("Authenticated user must not be null to use lookup cache!");
+
+                _memberLookupCache = await _repo.GetSystemMembers((SystemId)systemId).ToListAsync();
+            }
+
+            return _memberLookupCache.FirstOrDefault(x => x.Hid == memberRef || x.Uuid.ToString() == memberRef);
+        }
+
         if (Guid.TryParse(memberRef, out var guid))
-            return _repo.GetMemberByGuid(guid);
+            return await _repo.GetMemberByGuid(guid);
 
         if (_shortIdRegex.IsMatch(memberRef))
-            return _repo.GetMemberByHid(memberRef);
+            return await _repo.GetMemberByHid(memberRef);
 
-        return Task.FromResult<PKMember?>(null);
+        return null;
     }
 
-    protected Task<PKGroup?> ResolveGroup(string groupRef)
+    protected async Task<PKGroup?> ResolveGroup(string groupRef, bool cache = true)
     {
+        if (cache)
+        {
+            if (_groupLookupCache == null)
+            {
+                HttpContext.Items.TryGetValue("SystemId", out var systemId);
+                if (systemId == null)
+                    throw new Exception("Authenticated user must not be null to use lookup cache!");
+
+                _groupLookupCache = await _repo.GetSystemGroups((SystemId)systemId).ToListAsync();
+            }
+
+            return _groupLookupCache.FirstOrDefault(x => x.Hid == groupRef || x.Uuid.ToString() == groupRef);
+        }
+
         if (Guid.TryParse(groupRef, out var guid))
-            return _repo.GetGroupByGuid(guid);
+            return await _repo.GetGroupByGuid(guid);
 
         if (_shortIdRegex.IsMatch(groupRef))
-            return _repo.GetGroupByHid(groupRef);
+            return await _repo.GetGroupByHid(groupRef);
 
-        return Task.FromResult<PKGroup?>(null);
+        return null;
     }
 
     protected LookupContext ContextFor(PKSystem system)
diff --git a/PluralKit.API/Controllers/v2/GroupMemberControllerV2.cs b/PluralKit.API/Controllers/v2/GroupMemberControllerV2.cs
index 4a31d147..99ba21f8 100644
--- a/PluralKit.API/Controllers/v2/GroupMemberControllerV2.cs
+++ b/PluralKit.API/Controllers/v2/GroupMemberControllerV2.cs
@@ -53,7 +53,7 @@ public class GroupMemberControllerV2: PKControllerBase
         foreach (var JmemberRef in memberRefs)
         {
             var memberRef = JmemberRef.Value<string>();
-            var member = await ResolveMember(memberRef);
+            var member = await ResolveMember(memberRef, cache: true);
 
             // todo: have a list of these errors instead of immediately throwing
 
@@ -93,7 +93,7 @@ public class GroupMemberControllerV2: PKControllerBase
         foreach (var JmemberRef in memberRefs)
         {
             var memberRef = JmemberRef.Value<string>();
-            var member = await ResolveMember(memberRef);
+            var member = await ResolveMember(memberRef, cache: true);
 
             if (member == null)
                 throw Errors.MemberNotFoundWithRef(memberRef);
@@ -124,7 +124,7 @@ public class GroupMemberControllerV2: PKControllerBase
         foreach (var JmemberRef in memberRefs)
         {
             var memberRef = JmemberRef.Value<string>();
-            var member = await ResolveMember(memberRef);
+            var member = await ResolveMember(memberRef, cache: true);
 
             if (member == null)
                 throw Errors.MemberNotFoundWithRef(memberRef);
@@ -182,7 +182,7 @@ public class GroupMemberControllerV2: PKControllerBase
         foreach (var JgroupRef in groupRefs)
         {
             var groupRef = JgroupRef.Value<string>();
-            var group = await ResolveGroup(groupRef);
+            var group = await ResolveGroup(groupRef, cache: true);
 
             if (group == null)
                 throw Errors.GroupNotFound;
@@ -220,7 +220,7 @@ public class GroupMemberControllerV2: PKControllerBase
         foreach (var JgroupRef in groupRefs)
         {
             var groupRef = JgroupRef.Value<string>();
-            var group = await ResolveGroup(groupRef);
+            var group = await ResolveGroup(groupRef, cache: true);
 
             if (group == null)
                 throw Errors.GroupNotFoundWithRef(groupRef);
@@ -251,7 +251,7 @@ public class GroupMemberControllerV2: PKControllerBase
         foreach (var JgroupRef in groupRefs)
         {
             var groupRef = JgroupRef.Value<string>();
-            var group = await ResolveGroup(groupRef);
+            var group = await ResolveGroup(groupRef, cache: true);
 
             if (group == null)
                 throw Errors.GroupNotFoundWithRef(groupRef);