Azure Cosmos DB for MongoDB (4.2 server version): Supported features and syntax


Azure Cosmos DB is the Microsoft globally distributed multi-model database service. Azure Cosmos DB offers multiple database APIs. You can communicate with Azure Cosmos DB for MongoDB by using any of the open-source MongoDB client drivers. Azure Cosmos DB for MongoDB supports the use of existing client drivers by adhering to the MongoDB wire protocol.

By using Azure Cosmos DB for MongoDB, you can enjoy the benefits of MongoDB that you're used to, with all of the enterprise capabilities that Azure Cosmos DB provides: global distribution, automatic sharding, availability and latency guarantees, encryption at rest, backups, and much more.

Protocol support

The supported operators and any limitations or exceptions are listed in this article. Any client driver that understands these protocols should be able to connect to Azure Cosmos DB for MongoDB. When you create Azure Cosmos DB for MongoDB accounts, the 3.6+ version of accounts has an endpoint in the format * The 3.2 version of accounts has an endpoint in the format *


This article lists only the supported server commands, and excludes client-side wrapper functions. Client-side wrapper functions such as deleteMany() and updateMany() internally use the delete() and update() server commands. Functions that use supported server commands are compatible with Azure Cosmos DB for MongoDB.

Query language support

Azure Cosmos DB for MongoDB provides comprehensive support for MongoDB query language constructs. In the following sections, you can find the detailed list of currently supported operations, operators, stages, commands, and options.

Database commands

Azure Cosmos DB for MongoDB supports the following database commands.

Query and write operation commands

Command Supported
change streams Yes
delete Yes
eval No
find Yes
findAndModify Yes
getLastError Yes
getMore Yes
getPrevError No
insert Yes
parallelCollectionScan No
resetError No
update Yes

Transaction commands


Multi-document transactions are supported only within a single non-sharded collection. Cross-collection and cross-shard multi-document transactions are not yet supported in the API for MongoDB.

Command Supported
abortTransaction Yes
commitTransaction Yes

Authentication commands

Command Supported
authenticate Yes
getnonce Yes
logout Yes

Administration commands

Command Supported
cloneCollectionAsCapped No
collMod No
connectionStatus No
convertToCapped No
copydb No
create Yes
createIndexes Yes
currentOp Yes
drop Yes
dropDatabase Yes
dropIndexes Yes
filemd5 Yes
killCursors Yes
killOp No
listCollections Yes
listDatabases Yes
listIndexes Yes
reIndex Yes
renameCollection No

Diagnostics commands

Command Supported
buildInfo Yes
collStats Yes
connPoolStats No
connectionStatus No
dataSize No
dbHash No
dbStats Yes
explain Yes
features No
hostInfo Yes
listDatabases Yes
listCommands No
profiler No
serverStatus No
top No
whatsmyuri Yes

Aggregation pipeline

Azure Cosmos DB for MongoDB supports the following aggregation commands.

Aggregation commands

Command Supported
aggregate Yes
count Yes
distinct Yes
mapReduce No

Aggregation stages

Command Supported
addFields Yes
bucket No
bucketAuto No
changeStream Yes
collStats No
count Yes
currentOp No
facet Yes
geoNear Yes
graphLookup No
group Yes
indexStats No
limit Yes
listLocalSessions No
listSessions No
lookup Partial
match Yes
merge Yes
out Yes
planCacheStats Yes
project Yes
redact Yes
regexFind Yes
regexFindAll Yes
regexMatch Yes
replaceRoot Yes
replaceWith Yes
sample Yes
set Yes
skip Yes
sort Yes
sortByCount Yes
unset Yes
unwind Yes


The $lookup aggregation does not yet support the uncorrelated subqueries feature that's introduced in server version 3.6. If you attempt to use the $lookup operator with the let and pipeline fields, an error message that indicates that let is not supported appears.

Boolean expressions

Command Supported
and Yes
not Yes
or Yes

Conversion expressions

Command Supported
convert Yes
toBool Yes
toDate Yes
toDecimal Yes
toDouble Yes
toInt Yes
toLong Yes
toObjectId Yes
toString Yes

Set expressions

Command Supported
setEquals Yes
setIntersection Yes
setUnion Yes
setDifference Yes
setIsSubset Yes
anyElementTrue Yes
allElementsTrue Yes

Comparison expressions


The API for MongoDB does not support comparison expressions that have an array literal in the query.

Command Supported
cmp Yes
eq Yes
gt Yes
gte Yes
lt Yes
lte Yes
ne Yes
in Yes
nin Yes

Arithmetic expressions

Command Supported
abs Yes
add Yes
ceil Yes
divide Yes
exp Yes
floor Yes
ln Yes
log Yes
log10 Yes
mod Yes
multiply Yes
pow Yes
round Yes
sqrt Yes
subtract Yes
trunc Yes

Trigonometry expressions

Command Supported
acos Yes
acosh Yes
asin Yes
asinh Yes
atan Yes
atan2 Yes
atanh Yes
cos Yes
cosh Yes
degreesToRadians Yes
radiansToDegrees Yes
sin Yes
sinh Yes
tan Yes
tanh Yes

String expressions

Command Supported
concat Yes
indexOfBytes Yes
indexOfCP Yes
ltrim Yes
rtrim Yes
trim Yes
split Yes
strLenBytes Yes
strLenCP Yes
strcasecmp Yes
substr Yes
substrBytes Yes
substrCP Yes
toLower Yes
toUpper Yes

Text search operator

Command Supported
meta No

Array expressions

Command Supported
arrayElemAt Yes
arrayToObject Yes
concatArrays Yes
filter Yes
indexOfArray Yes
isArray Yes
objectToArray Yes
range Yes
reverseArray Yes
reduce Yes
size Yes
slice Yes
zip Yes
in Yes

Variable operators

Command Supported
map Yes
let Yes

System variables

Command Supported
$$KEEP Yes
$$NOW Yes
$$ROOT Yes

Literal operator

Command Supported
literal Yes

Date expressions

Command Supported
dayOfYear Yes
dayOfMonth Yes
dayOfWeek Yes
year Yes
month Yes
week Yes
hour Yes
minute Yes
second Yes
millisecond Yes
dateToString Yes
isoDayOfWeek Yes
isoWeek Yes
dateFromParts Yes
dateToParts Yes
dateFromString Yes
isoWeekYear Yes

Conditional expressions

Command Supported
cond Yes
ifNull Yes
switch Yes

Data type operator

Command Supported
type Yes

Accumulator expressions

Command Supported
sum Yes
avg Yes
first Yes
last Yes
max Yes
min Yes
push Yes
addToSet Yes
stdDevPop Yes
stdDevSamp Yes

Merge operator

Command Supported
mergeObjects Yes

Data types

Azure Cosmos DB for MongoDB supports documents that are encoded in MongoDB BSON format. Versions 4.0 and later (4.0+) enhance the internal usage of this format to improve performance and reduce costs. Documents that are written or updated through an endpoint running 4.0+ benefit from this optimization.

In an upgrade scenario, documents that were written prior to the upgrade to version 4.0+ won't benefit from the enhanced performance until they're updated via a write operation through the 4.0+ endpoint.

16-MB document support raises the size limit for your documents from 2 MB to 16 MB. This limit applies only to collections that are created after this feature is enabled. When this feature is enabled for your database account, it can't be disabled.

To enable 16-MB document support, change the setting on the Features tab for the resource in the Azure portal or programmatically add the EnableMongo16MBDocumentSupport capability.

We recommend that you enable Server Side Retry and avoid using wildcard indexes to ensure that requests in larger documents succeed. Raising your database or collection request units might also help performance.

Command Supported
Double Yes
String Yes
Object Yes
Array Yes
Binary Data Yes
ObjectId Yes
Boolean Yes
Date Yes
Null Yes
32-bit Integer (int) Yes
Timestamp Yes
64-bit Integer (long) Yes
MinKey Yes
MaxKey Yes
Decimal128 Yes
Regular Expression Yes
JavaScript Yes
JavaScript (with scope) Yes
Undefined Yes

Indexes and index properties

Azure Cosmos DB for MongoDB supports the following index commands and index properties.


Command Supported
Single Field Index Yes
Compound Index Yes
Multikey Index Yes
Text Index No
2dsphere Yes
2d Index No
Hashed Index No

Index properties

Command Supported
Unique Yes
Partial Supported only for unique indexes
Case Insensitive No
Sparse No
Background Yes


Azure Cosmos DB for MongoDB supports the following operators.

Logical operators

Command Supported
or Yes
and Yes
not Yes
nor Yes

Element operators

Command Supported
exists Yes
type Yes

Evaluation query operators

Command Supported
expr Yes
jsonSchema No
mod Yes
regex Yes
text No (Not supported. Use $regex instead.)
where No

In $regex queries, left-anchored expressions allow index search. However, using the i modifier (case-insensitivity) and the m modifier (multiline) causes the collection to scan in all expressions.

When there's a need to include $ or |, it's best to create two (or more) $regex queries.

For example, change the following original query:

find({x:{$regex: /^abc$/})

To this query:

find({x:{$regex: /^abc/, x:{$regex:/^abc$/}})

The first part of the modified query uses the index to restrict the search to documents that begin with ^abc. The second part of the query matches the exact entries. The bar operator (|) acts as an "or" function. The query find({x:{$regex: /^abc |^def/}) matches the documents in which field x has values that begin with abc or def. To use the index, we recommend that you break the query into two different queries that are joined by the $or operator: find( {$or : [{x: $regex: /^abc/}, {$regex: /^def/}] }).

Array operators

Command Supported
all Yes
elemMatch Yes
size Yes

Comment operator

Command Supported
comment Yes

Projection operators

Command Supported
elemMatch Yes
meta No
slice Yes

Update operators

Field update operators

Command Supported
inc Yes
mul Yes
rename Yes
setOnInsert Yes
set Yes
unset Yes
min Yes
max Yes
currentDate Yes

Array update operators

Command Supported
$ Yes
$[] Yes
$[\<identifier\>] Yes
addToSet Yes
pop Yes
pullAll Yes
pull Yes
push Yes
pushAll Yes

Update modifiers

Command Supported
each Yes
slice Yes
sort Yes
position Yes

Bitwise update operator

Command Supported
bit Yes
bitsAllSet No
bitsAnySet No
bitsAllClear No
bitsAnyClear No

Geospatial operators

Operator Supported
$geoWithin Yes
$geoIntersects Yes
$near Yes
$nearSphere Yes
$geometry Yes
$minDistance Yes
$maxDistance Yes
$center No
$centerSphere No
$box No
$polygon No

Sort operations

When you use the findOneAndUpdate operation, sort operations on a single field are supported. Sort operations on multiple fields aren't supported.


The API for MongoDB supports various indexes to enable sorting on multiple fields, improve query performance, and enforce uniqueness.

Client-side field-level encryption

Client-level field encryption is a driver feature and is compatible with the API for MongoDB. Explicit encryption, in which the driver explicitly encrypts each field when it's written, is supported. Automatic encryption isn't supported. Explicit decryption and automatic decryption is supported.

The mongocryptd shouldn't be run because it isn't needed to perform any of the supported operations.


Azure Cosmos DB supports GridFS through any GridFS-compatible Mongo driver.


Azure Cosmos DB supports automatic, native replication at the lowest layers. This logic is also extended to achieve low-latency, global replication. Azure Cosmos DB doesn't support manual replication commands.

Retryable writes

The retryable writes feature enables MongoDB drivers to automatically retry certain write operations. The feature results in more stringent requirements for certain operations, which match MongoDB protocol requirements. With this feature enabled, update operations, including deletes, in sharded collections require the shard key to be included in the query filter or update statement.

For example, with a sharded collection that's sharded on the "country" key, to delete all the documents that have the field "city" = "NYC", the application needs to execute the operation for all shard key ("country") values if the retryable writes feature is enabled.

  • db.coll.deleteMany({"country": "USA", "city": "NYC"}) - Success
  • db.coll.deleteMany({"city": "NYC"}) - Fails with error ShardKeyNotFound(61)


Retryable writes does not support bulk unordered writes at this time. If you want to perform bulk writes with retryable writes enabled, perform bulk ordered writes.

To enable the feature, add the EnableMongoRetryableWrites capability to your database account. This feature can also be enabled on the Features tab in the Azure portal.


Azure Cosmos DB supports automatic, server-side sharding. It automatically manages shard creation, placement, and balancing. Azure Cosmos DB doesn't support manual sharding commands, which means that you don't have to invoke commands like addShard, balancerStart, and moveChunk. You need to specify the shard key only when you create the containers or query the data.


Azure Cosmos DB doesn't yet support server-side sessions commands.

Time to Live

Azure Cosmos DB supports a Time to Live (TTL) that's based on the time stamp of the document. You can enable TTL for a collection in the Azure portal.

Custom TTL

This feature provides the ability to set a custom TTL on any one field in a collection.

On a collection that has TTL enabled on a field:

  • Acceptable types are the BSON data type and numeric types (integer, long, or double), which will be interpreted as a Unix millisecond time stamp to determine expiration.

  • If the TTL field is an array, then the smallest element of the array that is of an acceptable type is considered for document expiry.

  • If the TTL field is missing from a document, the document doesn’t expire.

  • If the TTL field isn't an acceptable type, the document doesn't expire.

Limitations of a custom TTL

  • Only one field in a collection can have a TTL set on it.

  • With a custom TTL field set, the \_ts field can't be used for document expiration.

  • You can't use the \_ts field in addition.


You can enable a custom TTL by updating the EnableTtlOnCustomPath capability for the account. Learn how to configure capabilities.

Set up the TTL

To set up the TTL, run this command: db.coll.createIndex({"YOUR_CUSTOM_TTL_FIELD":1}, {expireAfterSeconds: 10})


Multi-document transactions are supported within an unsharded collection. Multi-document transactions aren't supported across collections or in sharded collections. The timeout for transactions is a fixed 5 seconds.

Manage users and roles

Azure Cosmos DB doesn't yet support users and roles. However, Azure Cosmos DB supports Azure role-based access control (Azure RBAC) and read-write and read-only passwords and keys that can be obtained through the Azure portal (on the Connection Strings page).

Write concerns

Some applications rely on a write concern, which specifies the number of responses that are required during a write operation. Due to how Azure Cosmos DB handles replication in the background, all writes are automatically Quorum by default. Any write concern that's specified by the client code is ignored. Learn how to use consistency levels to maximize availability and performance.

Next steps