SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '99f327f53858b904bbf3d66c5d40f9b7388393afac6cbaed70eedad4efaf4592' 
  AND token = 'n2ansNmehAgHAc8BHr/WR0qqmop7czcnaNd3MtkqzN8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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