diff --git a/fdbclient/CommitTransaction.h b/fdbclient/CommitTransaction.h
index bc74941704..308c7f938c 100644
--- a/fdbclient/CommitTransaction.h
+++ b/fdbclient/CommitTransaction.h
@@ -80,6 +80,7 @@ struct MutationRef {
 	// This is stored this way for serialization purposes.
 	uint8_t type;
 	StringRef param1, param2;
+	bool clearSingleKey = false; // be only needed in client, so no serialization
 
 	MutationRef() {}
 	MutationRef( Type t, StringRef a, StringRef b ) : type(t), param1(a), param2(b) {}
diff --git a/fdbclient/Knobs.cpp b/fdbclient/Knobs.cpp
index 1903f5a5ef..9549626213 100644
--- a/fdbclient/Knobs.cpp
+++ b/fdbclient/Knobs.cpp
@@ -65,8 +65,8 @@ void ClientKnobs::initialize(bool randomize) {
 	init( BACKOFF_GROWTH_RATE,                     2.0 );
 	init( RESOURCE_CONSTRAINED_MAX_BACKOFF,       30.0 );
 	init( PROXY_COMMIT_OVERHEAD_BYTES,              23 ); //The size of serializing 7 tags (3 primary, 3 remote, 1 log router) + 2 for the tag length
-	init( DEFAULT_SMOOTH_AMOUNT,                    1.0);
-	init( INIT_MEAN_SHARD_BYTES,                  20000);
+	init( DEFAULT_SMOOTH_AMOUNT,                   5.0 );
+	init( INIT_MEAN_SHARD_BYTES,                  1024 );
 
 	init( TRANSACTION_SIZE_LIMIT,                  1e7 );
 	init( KEY_SIZE_LIMIT,                          1e4 );
@@ -230,7 +230,7 @@ void ClientKnobs::initialize(bool randomize) {
 	// transaction tags
 	init( MAX_TAGS_PER_TRANSACTION,                   5 );
 	init( MAX_TRANSACTION_TAG_LENGTH,                16 );
-	init( COMMIT_SAMPLE_BYTE,                     50000 );
+	init( COMMIT_SAMPLE_BYTE,                    100000 );
 	init( READ_TAG_SAMPLE_RATE,                    0.01 ); if( randomize && BUGGIFY ) READ_TAG_SAMPLE_RATE = 1.0; // Communicated to clients from cluster
 	init( TAG_THROTTLE_SMOOTHING_WINDOW,            2.0 );
 	init( TAG_THROTTLE_RECHECK_INTERVAL,            5.0 ); if( randomize && BUGGIFY ) TAG_THROTTLE_RECHECK_INTERVAL = 0.0;
diff --git a/fdbclient/NativeAPI.actor.cpp b/fdbclient/NativeAPI.actor.cpp
index c355aeb2ad..6dd067d595 100644
--- a/fdbclient/NativeAPI.actor.cpp
+++ b/fdbclient/NativeAPI.actor.cpp
@@ -2985,7 +2985,7 @@ void Transaction::clear( const KeyRef& key, bool addConflictRange ) {
 	data[key.size()] = 0;
 	t.mutations.emplace_back(req.arena, MutationRef::ClearRange, KeyRef(data, key.size()),
 	                         KeyRef(data, key.size() + 1));
-
+	t.mutations.back().clearSingleKey = true;
 	if(addConflictRange)
 		t.write_conflict_ranges.emplace_back(req.arena, KeyRef(data, key.size()), KeyRef(data, key.size() + 1));
 }
@@ -3272,13 +3272,18 @@ ACTOR Future<Optional<ClientTrCommitCostEstimation>> estimateCommitCosts(Transac
                                                                          CommitTransactionRef* transaction) {
 	state ClientTrCommitCostEstimation trCommitCosts;
 	state KeyRange keyRange;
-	for (int i = 0; i < transaction->mutations.size(); ++i) {
+	state int i = 0;
+	for (; i < transaction->mutations.size(); ++i) {
 		auto* it = &transaction->mutations[i];
 		if (it->type == MutationRef::Type::SetValue || it->isAtomicOp()) {
 			trCommitCosts.opsCount++;
 			trCommitCosts.writtenBytes += it->expectedSize();
 		} else if (it->type == MutationRef::Type::ClearRange) {
 			trCommitCosts.opsCount++;
+			if(it->clearSingleKey) {
+				trCommitCosts.clearIdxBytes.emplace(i, it->expectedSize()); // NOTE: whether we need a weight here?
+				continue;
+			}
 			keyRange = KeyRange(KeyRangeRef(it->param1, it->param2));
 			if (self->options.expensiveClearCostEstimation) {
 				StorageMetrics m = wait(self->getStorageMetrics(keyRange, std::numeric_limits<int>::max()));
diff --git a/fdbserver/Ratekeeper.actor.cpp b/fdbserver/Ratekeeper.actor.cpp
index 273c3a7399..e1f13b8120 100644
--- a/fdbserver/Ratekeeper.actor.cpp
+++ b/fdbserver/Ratekeeper.actor.cpp
@@ -1239,7 +1239,7 @@ void updateRate(RatekeeperData* self, RatekeeperLimits* limits) {
 	}
 }
 
-void updateCommitCostEstimation(RatekeeperData* self, TransactionTagMap<TransactionCommitCostEstimation> const& costEstimation) {
+void updateCommitCostEstimation(RatekeeperData* self, UIDTransactionTagMap<TransactionCommitCostEstimation> const& costEstimation) {
 //	if(self->validSS <= 0) return;
 //	int opsSum = 0;
 //	double bytesSum = 0;