SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '728fd9ca94a1b4d0c134b93b649503f7e4e8fd975fe795bf0fa76a173a294757' 
  AND token = 'ETUGmWZyH+0lXsEJinpGIGvmYE453tPB+oywWhFqG4Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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