diff --git a/docs/architecture.rst b/docs/architecture.rst
--- a/docs/architecture.rst
+++ b/docs/architecture.rst
@@ -10,7 +10,7 @@
 
 Each of these internal APIs have a dedicated (Postgresql) database.
 
-A global view of this architecture looks like:
+A global (and incomplete) view of this architecture looks like:
 
 .. thumbnail:: images/general-architecture.svg
 
@@ -18,7 +18,7 @@
 
 The front API components are:
 
-- :ref:`Storage API <swh-storage>`
+- :ref:`Storage API <swh-storage>` (including the Metadata Storage)
 - :ref:`Deposit API <swh-deposit>`
 - :ref:`Vault API <swh-vault>`
 - :ref:`Indexer API <swh-indexer>`
@@ -44,24 +44,41 @@
   the content of the :term:`archive` to extract derived information (mimetype,
   etc.)
 
+- :term:`Vault <vault>`: this type of celery task is responsible for cooking a
+  compressed archive (zip or tgz) of an archived object (typically a directory
+  or a repository). Since this can be a rather long process, it is delegated to
+  an asynchronous (celery) task.
+
 
 Tasks
 -----
 
+Listers
++++++++
+
 The following sequence diagram shows the interactions between these components
 when a new forge needs to be archived. This example depicts the case of a
 gitlab_ forge, but any other supported source type would be very similar.
 
 .. thumbnail:: images/tasks-lister.svg
 
-As one might observe in this diagram, it does create two things:
+As one might observe in this diagram, it does two things:
 
-- it adds one :term:`origin` objects in the :term:`storage` database for each
-  source code repository, and
+- it ask the forge (a gitlab_ instance in this case) the list of known repositories, and
 
 - it insert one :term:`loader` task for each source code repository that will
   be in charge of importing the content of that repository.
 
+Note that most listers usually work in incremental mode, meaning they store in a
+dedicated database the current state of the listing of the forge. Then, on a subsequent
+executino of the lister, it will ask only for new repositories.
+
+Also note that if the lister inserts a new loading task for a repository for which a
+loading task already exists, the existing task will be updated (if needed) instead of
+creating a new task.
+
+Loaders
++++++++
 
 The sequence diagram below describe this second step of importing the content
 of a repository. Once again, we take the example of a git repository, but any