diff --git a/backend/data.ts b/backend/data.ts
index 27a8b0a..f3998db 100644
--- a/backend/data.ts
+++ b/backend/data.ts
@@ -132,8 +132,8 @@ export const put = (sector: DataSector, key: NID, data: AssFile | AssUser): Prom
 			} else {
 
 				// ? SQL
-				// todo: check existing
-				await MySql.put('assfiles', key, data);
+				if (!(await MySql.get('assfiles', key))) await MySql.put('assfiles', key, data);
+				else return reject(new Error(`File key ${key} already exists`))
 
 				// todo: modify users SQL files property
 			}
@@ -156,8 +156,8 @@ export const put = (sector: DataSector, key: NID, data: AssFile | AssUser): Prom
 			} else {
 
 				// ? SQL
-				// todo: check existing
-				await MySql.put('assusers', key, data);
+				if (!(await MySql.get('assusers', key))) await MySql.put('assusers', key, data);
+				else return reject(new Error(`User key ${key} already exists`));
 			}
 		}