address PR comments

execution/gethexec/express_lane_service.go

@@ -324,13 +324,18 @@ func (es *expressLaneService) sequenceExpressLaneSubmission(
 	}
 	roundInfo, _ := es.roundInfo.Get(msg.Round)
 
+	prev, exists := roundInfo.msgAndResultBySequenceNumber[msg.SequenceNumber]
+
 	// Check if the submission nonce is too low.
 	if msg.SequenceNumber < roundInfo.sequence {
+		if exists && bytes.Equal(prev.msg.Signature, msg.Signature) {
+			return nil
+		}
 		return timeboost.ErrSequenceNumberTooLow
 	}
 
 	// Check if a duplicate submission exists already, and reject if so.
-	if prev, exists := roundInfo.msgAndResultBySequenceNumber[msg.SequenceNumber]; exists {
+	if exists {
 		if bytes.Equal(prev.msg.Signature, msg.Signature) {
 			return nil
 		}
@@ -342,7 +347,8 @@ func (es *expressLaneService) sequenceExpressLaneSubmission(
 	// Log an informational warning if the message's sequence number is in the future.
 	if msg.SequenceNumber > roundInfo.sequence {
 		if seqConfig.Timeboost.MaxQueuedTxCount != 0 &&
-			len(roundInfo.msgAndResultBySequenceNumber) >= seqConfig.Timeboost.MaxQueuedTxCount {
+			// Pending msgs count=(total msgs present in the map)-(number of processed messages=roundInfo.Sequence)
+			len(roundInfo.msgAndResultBySequenceNumber)-int(roundInfo.sequence) >= seqConfig.Timeboost.MaxQueuedTxCount {
 			return fmt.Errorf("reached limit for queuing of future sequence number transactions, please try again with the correct sequence number. Limit: %d, Current sequence number: %d", seqConfig.Timeboost.MaxQueuedTxCount, roundInfo.sequence)
 		}
 		log.Info("Received express lane submission with future sequence number", "SequenceNumber", msg.SequenceNumber)
@@ -360,7 +366,6 @@ func (es *expressLaneService) sequenceExpressLaneSubmission(
 		if !exists {
 			break
 		}
-		delete(roundInfo.msgAndResultBySequenceNumber, nextMsgAndResult.msg.SequenceNumber)
 		// Queued txs cannot use this message's context as it would lead to context canceled error once the result for this message is available and returned
 		// Hence using context.Background() allows unblocking of queued up txs even if current tx's context has errored out
 		var queueCtx context.Context

execution/gethexec/express_lane_service_test.go

@@ -386,19 +386,14 @@ func Test_expressLaneService_sequenceExpressLaneSubmission_outOfOrder(t *testing
 	require.Equal(t, 2, len(stubPublisher.publishedTxOrder))
 	els.roundInfoMutex.Lock()
 	roundInfo, _ := els.roundInfo.Get(0)
-	require.Equal(t, 3, len(roundInfo.msgAndResultBySequenceNumber)) // Processed txs are deleted
+	require.Equal(t, 5, len(roundInfo.msgAndResultBySequenceNumber))
 	els.roundInfoMutex.Unlock()
 
 	wg.Add(2) // 4 & 5 should be able to get in after 3 so we add a delta of 2
 	err := els.sequenceExpressLaneSubmission(ctx, buildValidSubmissionWithSeqAndTx(t, 0, 3, emptyTx))
 	require.NoError(t, err)
 	wg.Wait()
 	require.Equal(t, 5, len(stubPublisher.publishedTxOrder))
-
-	els.roundInfoMutex.Lock()
-	roundInfo, _ = els.roundInfo.Get(0)
-	require.Equal(t, 1, len(roundInfo.msgAndResultBySequenceNumber)) // Tx with seq num 10 should still be present
-	els.roundInfoMutex.Unlock()
 }
 
 func Test_expressLaneService_sequenceExpressLaneSubmission_erroredTx(t *testing.T) {