SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8aa54fdf3bb0efa80ecd95da3183b41e708256a9b6184c290353733ac91d6f1' 
  AND token = 'Eemdhjtir+Js/bCy6NR91OHhy8SMmTU84D45FpwzDJk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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