SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3f94abf488332fc4e76db498dbf193dd8731303f67e2126a016e9a0fde0c012' 
  AND token = 'VSg4XaSlV6+Sw0StUc2/fWAaD2BzWJGvooNtefIwOHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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