SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5968a6e223fdedf36165c1eee7766e5dd227edfaa62eee2598e60de5314bf95' 
  AND token = 'Ul/rVMnzZy2EjTWwrV+WRG3k0RdWit8agBCCnyXtNlo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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