From e1ef342a615c3cb296f449fe4b6528785329a265 Mon Sep 17 00:00:00 2001
From: Jian Guan <61915096+tdq45gj@users.noreply.github.com>
Date: Tue, 7 Apr 2026 13:05:58 -0400
Subject: [PATCH] Update buffered_bulk.go

---
 common/db/buffered_bulk.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/common/db/buffered_bulk.go b/common/db/buffered_bulk.go
index d0cb922a7..3b68a525b 100644
--- a/common/db/buffered_bulk.go
+++ b/common/db/buffered_bulk.go
@@ -77,8 +77,10 @@ func newBufferedBulkInserter(
 		docLimit:      docLimit,
 		// We set the byte limit to be slightly lower than maxMessageSizeBytes so it can fit in one OP_MSG.
 		// This may not always be perfect, e.g. we don't count update selectors in byte totals, but it should
-		// be good enough to keep memory consumption in check.
-		byteLimit:          MAX_MESSAGE_SIZE_BYTES - 100,
+		// be good enough to keep memory consumption in check. Because we cannot reliably predict the total
+		// size of the message that will be sent by the go-driver, the 1MB buffer for message overhead is
+		// a conservative estimate chosen arbitrarily.
+		byteLimit:          MAX_MESSAGE_SIZE_BYTES - 1_000_000,
 		writeModels:        make([]mongo.WriteModel, 0, docLimit),
 		canDoZeroTimestamp: zeroTimestampOk,
 	}