Question: We are looking to roll out a deployment of Sitecore 9.0.2 in CMS only mode. Does it need all databases to run or can it work off:

* Core
* Master
* Web

I'm happy we can run session inProc (provided thats still a thing in sc9) but do we need e.g. exm.master, experienceforms, messaging and reporting?

We don't plan to use either exm or the forms module atm.

Answer: 
That would be an XM environment.
You require: forms, core, web and master

<https://doc.sitecore.net/sitecore_experience_platform/setting_up_and_maintaining/sitecore_on_azure/deploying/sitecore_configurations_and_topology_for_azure#_XMSingle>

[![enter image description here](https://i.stack.imgur.com/WJFXC.png)](https://i.stack.imgur.com/WJFXC.png)
I unziped the WDP zip file and I verify connection string file :

Looks like you need next connection strings : 

```
<?xml version="1.0" encoding="utf-8"?>
<connectionStrings>
  <!-- 
    Sitecore connection strings.
    All database connections for Sitecore are configured here.
  -->
  <add name="core" connectionString="user id=user;password=password;Data Source=(server);Database=Sitecore_Core"/>
  <add name="master" connectionString="user id=user;password=password;Data Source=(server);Database=Sitecore_Master"/>
  <add name="web" connectionString="user id=user;password=password;Data Source=(server);Database=Sitecore_Web"/>
  <add name="sessions" connectionString="user id=sa;password=12345;data source=.\SQL2016;database=Sitecore_Sitecore.Sessions"/>
  <add name="experienceforms" connectionString="user id=user;password=password;Data Source=(server);Database=Sitecore_ExperienceForms"/>

</connectionStrings>

```

EXM works just in XP mode, you need reporting just in XP mode.