SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15b8e3b1281585321d4ff52a58bd947ded12b550d802e849f171ae1cf5ac5097' 
  AND token = 'IWLkEq3jrStsVaMMJF/tol7JRX1cphRhgYPMPOqrhNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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