MongoDB operations

The Nimbus MongoDB endpoint implements a defined subset of the MongoDB command surface. Anything outside this page is rejected with an explicit error — an unknown command returns CommandNotFound (code 59), and an unsupported operator inside a supported command returns an error naming the operator. Nothing is silently ignored.

Commands

Handshake and diagnostics — no authentication required

Command	Notes
`hello`, `isMaster`	Reports a standalone, writable server
`buildInfo`	Reports server version `7.0.0`
`ping`
`whatsmyuri`
`getParameter`
`serverStatus`
`connectionStatus`
`getCmdLineOpts`
`getFreeMonitoringStatus`
`getLog`

Authentication

Command	Notes
`saslStart`	SCRAM-SHA-256 only; other mechanisms are rejected
`saslContinue`

Every command below this point requires an authenticated connection.

CRUD

Command	Notes
`insert`	Creates the collection (and tenant) on first use
`find`	See filter operators
`update`	See update operators; supports upsert
`delete`
`findAndModify`
`count`
`distinct`

Aggregation

Command	Notes
`aggregate`	See aggregation pipeline; `$changeStream` pipelines are rejected with `CommandNotSupported`

Collections and databases

Command	Notes
`create`
`drop`
`listCollections`
`listDatabases`

Indexes

Command	Notes
`createIndexes`
`dropIndexes`
`listIndexes`

Cursors

Command	Notes
`getMore`
`killCursors`

Sessions and transactions

Command	Notes
`startSession`	At most 128 concurrent sessions per connection
`endSessions`
`refreshSessions`
`commitTransaction`	A conflicting concurrent write fails the commit with `WriteConflict`
`abortTransaction`

Transactions are started with the standard startTransaction: true field on the first operation in the session. A transaction is scoped to one database (one Nimbus tenant).

Filter operators

Supported in find, update, delete, findAndModify, count, and $match:

Operator	Meaning
implicit equality	`{ field: value }`
`$eq`	equals
`$ne`	not equals
`$gt`	greater than
`$gte`	greater than or equal
`$lt`	less than
`$lte`	less than or equal

All other filter operators — including $in, $nin, $or, $and, $not, $nor, $regex, and $exists — are rejected with a BadValue error naming the operator. Top-level $-prefixed keys in a filter are likewise rejected.

Update operators

Operator	Notes
`$set`
`$unset`
`$rename`
`$setOnInsert`	Applied only on upsert-insert
`$currentDate`
`$inc`
`$min`
`$max`
`$mul`
`$addToSet`	Supports `$each`
`$push`	Supports `$each`
`$pull`
`$pullAll`
`$pop`
`$bit`

Aggregation pipeline

Stages

Stage	Notes
`$match`	Same operator surface as filter operators
`$sort`
`$limit`
`$skip`
`$project`
`$addFields`
`$count`
`$group`	See accumulators below
`$unwind`

An unrecognized stage fails the pipeline with an error naming the stage. $changeStream is rejected with CommandNotSupported — change streams are not available through the MongoDB endpoint.

`$group` accumulators

Accumulator
`$sum`
`$avg`
`$min`
`$max`
`$first`
`$last`
`$push`
`$addToSet`

Server identity and limits

Property	Value
Reported server version	`7.0.0`
Wire protocol versions	0–21 (`OP_MSG`)
Max BSON document size	16,777,216 bytes (16 MiB)
Max message size	48,000,000 bytes
Max write batch size	100,000 operations
Logical session timeout	30 minutes
Network binding	Loopback only; non-loopback binds are refused