diff --git a/clang-tools-extra/clangd/index/remote/Client.cpp b/clang-tools-extra/clangd/index/remote/Client.cpp
--- a/clang-tools-extra/clangd/index/remote/Client.cpp
+++ b/clang-tools-extra/clangd/index/remote/Client.cpp
@@ -55,6 +55,8 @@
     llvm::BumpPtrAllocator Arena;
     llvm::UniqueStringSaver Strings(Arena);
     ReplyT Reply;
+    unsigned Received = 0;
+    unsigned FailedToParse = 0;
     while (Reader->Read(&Reply)) {
       if (!Reply.has_stream_result()) {
         FinalResult = Reply.final_result();
@@ -64,11 +66,15 @@
           fromProtobuf(Reply.stream_result(), &Strings, ProjectRoot);
       if (!Response) {
         elog("Received invalid {0}", ReplyT::descriptor()->name());
+        ++FailedToParse;
         continue;
       }
       Callback(*Response);
+      ++Received;
     }
-    SPAN_ATTACH(Tracer, "status", Reader->Finish().ok());
+    SPAN_ATTACH(Tracer, "Status", Reader->Finish().ok());
+    SPAN_ATTACH(Tracer, "Received", Received);
+    SPAN_ATTACH(Tracer, "Failed to parse", FailedToParse);
     return FinalResult;
   }
 
diff --git a/clang-tools-extra/clangd/index/remote/server/Server.cpp b/clang-tools-extra/clangd/index/remote/server/Server.cpp
--- a/clang-tools-extra/clangd/index/remote/server/Server.cpp
+++ b/clang-tools-extra/clangd/index/remote/server/Server.cpp
@@ -9,6 +9,8 @@
 #include "index/Index.h"
 #include "index/Serialization.h"
 #include "index/remote/marshalling/Marshalling.h"
+#include "support/Logger.h"
+#include "support/Trace.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Path.h"
@@ -57,21 +59,32 @@
   grpc::Status Lookup(grpc::ServerContext *Context,
                       const LookupRequest *Request,
                       grpc::ServerWriter<LookupReply> *Reply) override {
+    trace::Span Tracer("Remote index server Lookup");
+    SPAN_ATTACH(Tracer, "LookupRequest", Request->ShortDebugString());
     clangd::LookupRequest Req;
     for (const auto &ID : Request->ids()) {
       auto SID = SymbolID::fromStr(StringRef(ID));
-      if (!SID)
+      if (!SID) {
+        elog("Lookup request cancelled: invalid SymbolID {1}", SID.takeError());
         return grpc::Status::CANCELLED;
+      }
       Req.IDs.insert(*SID);
     }
+    unsigned Sent = 0;
+    unsigned FailedToSend = 0;
     Index->lookup(Req, [&](const clangd::Symbol &Sym) {
       auto SerializedSymbol = toProtobuf(Sym, IndexedProjectRoot);
-      if (!SerializedSymbol)
+      if (!SerializedSymbol) {
+        ++FailedToSend;
         return;
+      }
       LookupReply NextMessage;
       *NextMessage.mutable_stream_result() = *SerializedSymbol;
       Reply->Write(NextMessage);
+      ++Sent;
     });
+    SPAN_ATTACH(Tracer, "Sent", Sent);
+    SPAN_ATTACH(Tracer, "Failed to send", FailedToSend);
     LookupReply LastMessage;
     LastMessage.set_final_result(true);
     Reply->Write(LastMessage);
@@ -81,15 +94,24 @@
   grpc::Status FuzzyFind(grpc::ServerContext *Context,
                          const FuzzyFindRequest *Request,
                          grpc::ServerWriter<FuzzyFindReply> *Reply) override {
+    trace::Span Tracer("Remote index server FuzzyFind");
+    SPAN_ATTACH(Tracer, "FuzzyFindRequest", Request->ShortDebugString());
     const auto Req = fromProtobuf(Request, IndexedProjectRoot);
+    unsigned Sent = 0;
+    unsigned FailedToSend = 0;
     bool HasMore = Index->fuzzyFind(Req, [&](const clangd::Symbol &Sym) {
       auto SerializedSymbol = toProtobuf(Sym, IndexedProjectRoot);
-      if (!SerializedSymbol)
+      if (!SerializedSymbol) {
+        ++FailedToSend;
         return;
+      }
       FuzzyFindReply NextMessage;
       *NextMessage.mutable_stream_result() = *SerializedSymbol;
       Reply->Write(NextMessage);
+      ++Sent;
     });
+    SPAN_ATTACH(Tracer, "Sent", Sent);
+    SPAN_ATTACH(Tracer, "Failed to send", FailedToSend);
     FuzzyFindReply LastMessage;
     LastMessage.set_final_result(HasMore);
     Reply->Write(LastMessage);
@@ -98,21 +120,32 @@
 
   grpc::Status Refs(grpc::ServerContext *Context, const RefsRequest *Request,
                     grpc::ServerWriter<RefsReply> *Reply) override {
+    trace::Span Tracer("Remote index server Refs");
+    SPAN_ATTACH(Tracer, "RefsRequest", Request->ShortDebugString());
     clangd::RefsRequest Req;
     for (const auto &ID : Request->ids()) {
       auto SID = SymbolID::fromStr(StringRef(ID));
-      if (!SID)
+      if (!SID) {
+        elog("Refs request cancelled: invalid SymbolID {1}", SID.takeError());
         return grpc::Status::CANCELLED;
+      }
       Req.IDs.insert(*SID);
     }
+    unsigned Sent = 0;
+    unsigned FailedToSend = 0;
     bool HasMore = Index->refs(Req, [&](const clangd::Ref &Reference) {
       auto SerializedRef = toProtobuf(Reference, IndexedProjectRoot);
-      if (!SerializedRef)
+      if (!SerializedRef) {
+        ++FailedToSend;
         return;
+      }
       RefsReply NextMessage;
       *NextMessage.mutable_stream_result() = *SerializedRef;
       Reply->Write(NextMessage);
+      ++Sent;
     });
+    SPAN_ATTACH(Tracer, "Sent", Sent);
+    SPAN_ATTACH(Tracer, "Failed to send", FailedToSend);
     RefsReply LastMessage;
     LastMessage.set_final_result(HasMore);
     Reply->Write(LastMessage);