SELECT 
  COUNT(DISTINCT cv.video_id) 
FROM 
  cscart_cp_videos cv 
  LEFT JOIN cscart_cp_video_descriptions cvd ON cvd.video_id = cv.video_id 
  AND cvd.lang_code = 'en' 
WHERE 
  1 
  AND cv.video_id IN (210) 
  AND cv.status = 'A'

Query time 0.00022

JSON explain

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

Result

COUNT(DISTINCT cv.video_id)
0