ZODB chapter

docs/backend/zodb.md

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 myst:
   html_meta:
-    "description": ""
-    "property=og:description": ""
-    "property=og:title": ""
-    "keywords": ""
+    "description": "Zope Object Database (ZODB)"
+    "property=og:description": "Zope Object Database (ZODB)"
+    "property=og:title": "Zope Object Database (ZODB)"
+    "keywords": "Plone, ZODB, Zope Object Database, RelStorage, ZEO, ZODB Extension Objects"
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+% TODO: Diátaxis conceptual guide
+
 (backend-zodb-label)=
 
-# ZODB
+# Zope Object Database (ZODB)
+
+The {term}`Zope Object Database` (ZODB) is a Python native, object-oriented database designed for direct persistence of Python objects.
+Unlike traditional relational databases that rely on tables and SQL queries, ZODB allows developers to work directly with Python objects, persisting them without the need for object-relational mapping (ORM).
+
+
+## Core features of ZODB
+
+Transparent persistence
+: Objects stored in ZODB automatically persist.
+  In a Plone request/response cycle, they do not require an explicit save or commit operation, since this is done automatically.
+
+No schema constraints
+: Unlike relational databases, ZODB does not require predefined schemas, allowing for flexible and dynamic data structures.
+  The attributes of the Python objects themselves are stored.
+
+ACID compliance
+: ZODB ensures data consistency through transactions that support atomicity, consistency, isolation, and durability (ACID).
+
+Automatic conflict resolution
+: With its multi-version concurrency control (MVCC), ZODB can handle concurrent access efficiently.
+
+Built-in versioning and undo
+: The database allows versioning, enabling rollback to previous states if needed.
+
+Scalability
+: ZODB can be used in standalone applications or scaled with {term}`ZODB Extension Objects` (ZEO) for distributed storage.
+  Additionally, ZODB supports the {term}`RelStorage` adapter, which allows it to use relational databases, including PostgreSQL, MySQL, or Oracle, as a backend, providing flexibility for integration with existing database infrastructures.
+
+
+## How ZODB works
+
+At its core, ZODB operates as an object store, maintaining serialized Python objects with some metadata in a hierarchical structure.
+
+Storage
+: Handles how objects are stored on disk or in-memory.
+
+  The default storage is {term}`FileStorage`, which writes data to `.fs` files. `FileStorage` does not scale, as only one process can work with it.
+
+  {term}`ZEO` storage is used for distributed multi-client access to the same database, introducing scalability.
+
+  {term}`RelStorage` is another highly scalable option.
+  It allows ZODB to use relational databases like PostgreSQL, MySQL, or Oracle as backend storage, combining object persistence with traditional database infrastructure.
+  RelStorage is used often in a containerized deployment environment.
+
+Connection
+: Acts as the interface between Python applications and the database.
+  With ZEO for each active Zope thread, one connection is established.
+  Connections are pooled and re-used.
+
+Transaction manager
+: Manages transactional operations, ensuring data integrity.
+  A transaction normally starts with the request, and ends with the response.
+  However, in long-running requests with lots of database writes, transactions can be committed in between.
+
+Indexing and caching
+: Optimizes read and write operations for better performance.
+  Tuning the ZODB cache sizes to hardware environment and the kind of data stored may help to speed up the application.
+
+
+## Further reading
 
+More information can be found at the official [ZODB website](https://zodb.org/en/latest/).

docs/glossary.md

@@ -554,12 +554,21 @@ react-intl
 WSGI
     The Web Server Gateway Interface (WSGI, pronounced _WIZ-ghee_) is a simple calling convention for web servers to forward requests to web applications or frameworks written in the Python programming language.
 
+ZODB Extension Objects
 ZEO
     [ZEO](https://zeo.readthedocs.io/en/latest/) is a client-server storage for ZODB for sharing a single storage among many clients.
 
+Zope Object Database
 ZODB
     [A native object database for Python](https://zodb.org/en/latest/).
 
+`FileStorage`
+    `FileStorage` is a Python class in {term}`ZODB` that saves data in a file.    
+
+    ```{seealso}
+    https://zodb.org/en/latest/reference/storages.html#filestorage
+    ```
+
 Zope
     [Zope](https://zope.readthedocs.io/en/latest/) is a Python-based application server for building secure and highly scalable web applications.