SELECT 
  gallery_id, 
  placeholder, 
  no_pagination 
FROM 
  cscart_image_gallery_ext_settings 
WHERE 
  placeholder <> '' 
  AND status = 'A'

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}