SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '506a66f62c0571da661a9c3f3c60eb3fec3eb88f1df724481e5dade376f48c01' 
  AND token = 'Rx3qgSoSwbmxTYvUjQoW+SYtmxyPpvlhArOk3vDdxlQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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