SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b8d4077c21ab9418a107c450feb468a71454f29f2a9db560365ebcadefdad3' 
  AND token = '+DYmuHK+WgyW1bSPUGPmwXfhIERiOErBMnufmjOLeXk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}