diff --git a/README.md b/README.md
index 56c8d62..bd474df 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,6 @@ A temporary email service
 
 ## TODO
 
- - Use an DB other than sqlite. it is not good for concurrent operations.
  - Do not store the raw mail data in the DB, maybe use block storage (the provider can be a disk provider at first)
  - Use `bluemonday` to sanitize the mail html before rendering
  - Cache subject parsed from email. Then when listing the email it is not necessary to parse all mails and retrieve them.