diff --git a/migrations/2023_11_06_000001_drop_contests.py b/migrations/2023_11_06_000001_drop_contests.py
new file mode 100644
index 0000000..f10b239
--- /dev/null
+++ b/migrations/2023_11_06_000001_drop_contests.py
@@ -0,0 +1,15 @@
+import pymongo
+
+from . import MONGO_HOST, DATABASE
+
+
+def main():
+    client = pymongo.MongoClient(MONGO_HOST)
+    db = client[DATABASE]
+    collection = db['course']
+    collection.update_many({}, {'$unset': {'contests': 1}})
+    collection = db['problem']
+    collection.update_many({}, {'$unset': {'contests': 1}})
+
+
+main()
diff --git a/migrations/__init__.py b/migrations/__init__.py
new file mode 100644
index 0000000..de74105
--- /dev/null
+++ b/migrations/__init__.py
@@ -0,0 +1,4 @@
+import os
+
+MONGO_HOST = os.getenv('MONGO_HOST', 'mongomock://localhost')
+DATABASE = 'normal-oj'
diff --git a/pyproject.toml b/pyproject.toml
index bb2a0aa..96fd1b7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -16,6 +16,7 @@ PyJWT = "^2.5"
 requests = "^2.31"
 mosspy = "^1.0"
 redis = "^4.3"
+pymongo = "^4.5.0"
 
 [tool.poetry.group.dev.dependencies]
 pytest = "^7.1"