AWS documentdb documentation change

Service: documentdb · 2025-08-25 · Documentation low

File: documentdb/latest/developerguide/managing-indexes.md

Summary

Added new section explaining index bloat in Amazon DocumentDB with MVCC implementation details, diagnostic commands, and reIndex maintenance guidance

Security assessment

Documentation explains database maintenance procedures for storage optimization. While index bloat impacts performance and resource usage, there's no evidence this addresses a security vulnerability or introduces security features. The content focuses on operational efficiency rather than security controls

Diff

diff --git a/documentdb/latest/developerguide/managing-indexes.md b/documentdb/latest/developerguide/managing-indexes.md
index cbc4e9fc2..7dc6eacc1 100644
--- a//documentdb/latest/developerguide/managing-indexes.md
+++ b//documentdb/latest/developerguide/managing-indexes.md
@@ -192,0 +193,50 @@ The “currentIndexBuildName”, “msg”, and “progress” fields are not su
+###### Topics
+
+  * Index bloat
+
+  * Index maintenance using reIndex
+
+
+
+
+### Index bloat
+
+Amazon DocumentDB uses Multi-Version Concurrency Control (MVCC) to manage concurrent transactions. When documents are deleted or updated, their previous versions remain in collections and indexes as "dead" versions. The garbage collection process automatically reclaims space from these dead versions for future operations.
+
+Index bloat occurs when a collection's indexes become larger due to the accumulation of dead or obsolete index entries or fragmentation within the pages. The percentage reported represents the amount of index space that can be used by future index entries. This bloat consumes space in both the buffer cache and storage. If you want to remove the bloat, you will need to rebuild indexes.
+
+###### Example
+
+Run the following command to determine unused storage for your index:
+    
+    
+    db.coll.aggregate({$indexStats:{}});
+
+The result looks similar to this:
+    
+    
+    { 
+        "name" : "_id_",
+        "key" : { 
+            "_id" : 1 
+        },
+        "host" : "devbox-test.localhost.a2z.com:27317",
+        "size" : NumberLong(827392),
+        "accesses" : {
+            "ops" : NumberLong(40000),
+            "docsRead" : NumberLong(46049),
+            "since" : ISODate("2025-04-03T21:44:51.251Z") 
+        },
+        "cacheStats" : {
+            "blksRead" : NumberLong(264),
+            "blksHit" : NumberLong(140190),
+            "hitRatio" : 99.8121
+        }, 
+        "unusedStorageSize" : {
+            "unusedSizeBytes" : 409600,
+            "unusedSizePercent" : 49.51
+        }
+    }
+
+You can rebuild indexes without downtime using the `reIndex` command, which requires a scan of the entire collection. See Index maintenance using reIndex.
+