SELECT 
  cv.video_id, 
  cvd.video, 
  cvd.description, 
  cvd.short_description, 
  cvd.like_count, 
  cvd.comment_count, 
  cvd.youtube_id, 
  cv.status, 
  cv.user_id, 
  cv.community_thumbnail, 
  cv.community_video_url, 
  cv.community_url, 
  cu.firstname, 
  CASE WHEN MAX(mum.avatar) IS NOT NULL 
  AND MAX(mum.avatar) != '' THEN CONCAT(
    'https://cdn.kindlife.in/', 
    MAX(mum.avatar)
  ) ELSE 'https://cdn.kindlife.in/images/ui_icon/user-default.svg' END AS userAvatar 
FROM 
  cscart_cp_videos cv 
  LEFT JOIN cscart_cp_video_descriptions cvd ON cvd.video_id = cv.video_id 
  AND cvd.lang_code = 'en' 
  LEFT JOIN cscart_users cu ON cu.user_id = cv.user_id 
  LEFT JOIN kl_user_pref_master mum ON cv.user_id = mum.user_id 
WHERE 
  1 
  AND cv.video_id IN (210) 
  AND cv.status = 'A' 
GROUP BY 
  cv.video_id, 
  cvd.video, 
  cvd.description, 
  cvd.short_description, 
  cvd.like_count, 
  cvd.comment_count, 
  cv.status, 
  cv.user_id, 
  cv.community_thumbnail, 
  cv.community_video_url, 
  cu.firstname 
ORDER BY 
  FIELD(cv.video_id, 210) 
LIMIT 
  0, 5

Query time 0.00041

JSON explain

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