SELECT 
  wishlist_id 
FROM 
  cscart_ec_hb_vendor_favts 
WHERE 
  user_id = 0 
  AND FIND_IN_SET(15, blog_ids)

Query time 0.00022

JSON explain

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