SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3edb691316d7d41f623bbafc8a20ed12c745a40c63b994884824776b0e9e98a3' 
  AND token = 'ITWmsmyZfuRKJXUJRIRIhxcZo/CidujWAdRwDogI2Vc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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