Sandbox

SELECT 
  us.user_type, 
  us.timestamp, 
  pref.avatar, 
  pref.isExpert, 
  pref.expertDomains, 
  pref.order_success_cnt, 
  pref.prod_review_cnt, 
  JSON_EXTRACT(
    pref.new_user_preferences, '$.kindcrew'
  ) AS kindcrew, 
  pref.user_name, 
  pref.dob, 
  pref.blog_cnt, 
  pref.video_cnt, 
  pref.about, 
  pref.gender 
from 
  kl_user_pref_master pref 
  left join cscart_users us on pref.user_id = us.user_id 
WHERE 
  pref.user_id = 342027

Query time 0.00032

JSON explain

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