SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fcd1d273d4349bf82b16e389b9b5542538f9729b21a78d4c7cf15bb25747437d' 
  AND token = 'Jb9FV7/76vQo+jG6RzIoiUt2g6jhHo3XjWNnRhzKpQo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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