Update FAQ to indicate legacy opcodes were removed (#1593)

* Update FAQ to indicate legacy opcodes were removed

* Clarify usage of legacy opcodes

* Update source/server_write_commands.rst

Co-authored-by: Andreas Braun <[email protected]>

---------

Co-authored-by: Andreas Braun <[email protected]>

Author: alexbevi

source/server_write_commands.rst

@@ -467,7 +467,7 @@ FAQ
 Why are ``_id`` values generated client-side by default for new documents?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Though drivers may expose configuration options to prevent this behavior, by default a new ``ObjectId`` value will be created client-side before an insert or upsert operation. 
+Though drivers may expose configuration options to prevent this behavior, by default a new ``ObjectId`` value will be created client-side before an ``insert`` operation. 
 
 This design decision primarily stems from the fact that MongoDB is a distributed database and the typical unique auto-incrementing scalar value most RDBMS' use for generating a primary key would not be robust enough, necessitating the need for a more robust data type (``ObjectId`` in this case). These ``_id`` values can be generated either on the client or the server, however when done client-side a new document's ``_id`` value is immediately available for use without the need for a network round trip. 
 
@@ -477,10 +477,7 @@ Prior to MongoDB 3.6, an ``insert`` operation would use the  ``OP_INSERT`` opcod
 Can a driver still use the ``OP_INSERT``, ``OP_DELETE``, ``OP_UPDATE``?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Yes, a 2.6 server will still support those. But it is unlikely that a 2.8 server would.  Of course, when talking to older servers, the usual op codes will continue working the same. An older server is one that reports ``hello.maxWireVersion`` to be less than 2 or does not include the field.
-
-The rationale here is that we may choose to divert all the write traffic to the new
-protocol. (This depends on the having the overhead to issue a batch with one item very low.)
+The `legacy opcodes were removed in MongoDB 6.0 <https://www.mongodb.com/docs/manual/release-notes/6.0-compatibility/#legacy-opcodes-removed>`_. As of MongoDB 3.6 these opcodes were superseded by `OP_MSG <https://www.mongodb.com/docs/manual/reference/mongodb-wire-protocol/#op_msg>`_, however all server versions up until 6.0 continued to support the legacy opcodes.
 
 
 Can an application still issue requests with write concerns {w: 0}?
@@ -505,7 +502,8 @@ Yes but as of 2.6 the existing getLastError behavior is supported for backward c
 Changelog
 ---------
 
-:2024-06-04: Add FAQ entry outlining client-side _id value generation 
+:2024-06-04: Add FAQ entry outlining client-side _id value generation
+             Update FAQ to indicate legacy opcodes were removed
 :2022-10-05: Revise spec front matter and reformat changelog.
 :2022-07-25: Remove outdated value for ``maxWriteBatchSize``
 :2021-04-22: Updated to use hello command