SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d3b5aeb94d6954879a78c283c65d75b4e0953f50cc303a2f66e8f2f8ee79a59' 
  AND token = 'RCdXlW7jvsFi+FhWylzbznj+86VYaOqMY8xeY/V7lS4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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