diff --git a/README.md b/README.md
index 8abd43da..23cba15c 100644
--- a/README.md
+++ b/README.md
@@ -14,9 +14,22 @@ user.  These features include:
 * Clustered indexes (store Python pickles directly with index entries)
 * Bulk loading
 * Deletion
-* Disk serialization
+* ~~Disk serialization~~ [currently broken as of Jan 2024](https://github.com/Toblerity/rtree/pull/197)
 * Custom storage implementation (to implement spatial indexing in ZODB, for example)
 
+These features do not include:
+
+* Multithread safety (for reading or writing)
+* Multiprocess safety (for reading or writing)
+
+For either of these, we recommend using:
+
+* A PostGIS database, or
+* GeoPandas + spatial joining, or
+* Building an rtree from scratch in each thread/process (using [generator syntax](https://rtree.readthedocs.io/en/latest/performance.html#use-stream-loading))
+
+Note that since rtree is written in C, it can be orders of magnitude faster than a 
+database even if running sequentially.
 
 Wheels are available for most major platforms, and `rtree` with bundled `libspatialindex` can be installed via pip:
 
diff --git a/docs/source/index.rst b/docs/source/index.rst
index ec162c51..3bfb5f08 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -13,9 +13,23 @@ user.  These features include:
 * Clustered indexes (store Python pickles directly with index entries)
 * Bulk loading
 * Deletion
-* Disk serialization
+* Disk serialization (`currently broken as of Jan 2024`_)
 * Custom storage implementation (to implement spatial indexing in ZODB, for example)
 
+These features do not include:
+
+* Multithread safety (for reading or writing)
+* Multiprocess safety (for reading or writing)
+
+For either of these, we recommend using:
+
+* A PostGIS database, or
+* GeoPandas + spatial joining, or
+* Building an rtree from scratch in each thread/process (using [generator syntax](https://rtree.readthedocs.io/en/latest/performance.html#use-stream-loading))
+
+Note that since rtree is written in C, it can be orders of magnitude faster than a
+database even if running sequentially.
+
 Documentation
 ..............................................................................
 
@@ -34,6 +48,7 @@ Documentation
 * :ref:`modindex`
 * :ref:`search`
 
+.. _`currently broken as of Jan 2024`: https://github.com/Toblerity/rtree/pull/197
 .. _`R-trees`: https://en.wikipedia.org/wiki/R-tree
 .. _`ctypes`: https://docs.python.org/3/library/ctypes.html
 .. _`libspatialindex`: https://libspatialindex.org