docs(faqs): add entry to configure custom datastore_config in res_config

docs/faqs.md

@@ -26,4 +26,19 @@ cfg.default_worker.accounts.append(None)
 cfg.default_worker.default_account = None
 cfg.to_file(get_resconfig_loc())
 ```
-Then run `texts` again. Then use the [variable update](scl.md#dealing-with-failures) (using `:=`) to inforce re-evaluation of the resources. A simple `%rerun var` will not be sufficient.
\ No newline at end of file
+Then run `texts` again. Then use the [variable update](scl.md#dealing-with-failures) (using `:=`) to inforce re-evaluation of the resources. A simple `%rerun var` will not be sufficient.
+
+**Q**: How can I set a datastore configuration alternative to the default `$HOME/.fireworks/datastore_config.yaml`?
+
+**A**: This can be done using the [vre-middleware's](https://vre-middleware.readthedocs.io/en/latest/resconfig.html) Python API. For example, within an iPython command line session:
+```python
+from os import path
+from virtmat.middleware.resconfig import get_resconfig_loc, ResConfig, WorkerConfig
+cfg = ResConfig.from_file(get_resconfig_loc())
+wcfg = cfg.workers[0]
+wcfg.envvars = {'DATASTORE_CONFIG': '/alternative/path_to/my_project/datastore_config.yaml'}
+wcfg.default_envvars = ['DATASTORE_CONFIG']
+cfg.default_worker = wcfg
+cfg.to_file(get_resconfig_loc())
+
+```