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+# TODO
+
+  - encryption in Clouderver
+  - snapshots
+  - cleanup
+    - delete invalid versions by constructing the chain and deleting everything not on it
+    - delete old versions (older than some particular age, older than latest snapshot)
+    - delete old snapshots
+  - actions to build with various features enabled/disabled
+
+# CAS notes
+
+  compare_and_swap(name, old, new)
+  
+  S3: impossible
+  
+  Azure:
+   - read(name)
+   - if content != old, fail
+   - if not found, write new value unconditionally, start over with compare_and_swap(name, new, new)
+   - write with condition on etag from first step
+  
+  GCP:
+   - read(name)
+   - if content != old, fail
+   - write with condition on generation, or zero if not found