SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6e6c910be9110582eb502dacc1f6ce381184f18445f1c3a1abcff8a39b6a935' 
  AND token = 'Ug5xuQSCoWxW552yJ5VpzSSipJk51+renSpIXajvPFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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