SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15fa5591de34308f8596a20eb64776b491808ff3f29e924dcb5bfb1321adc7fc' 
  AND token = 'lM+ag/w1BYvxHcTM7qwYe+XJ4KGQDOsPyGfLNVOi0vM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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