SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6ac081d09abc6b7b7d561dbdcf1dbd320ef4402f579ca97e37885010985b2c8' 
  AND token = '50Vtb6C5XmJEWxKvJLsQAmxu78+nWCSQY4565F2OUU8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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