SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'vi' 
WHERE 
  pfv.variant_id IN (
    71637, 71636, 71635, 71634, 71633, 71632, 
    71638, 74647, 74648, 75520, 75519, 
    79251, 79252, 80381, 81655, 81656, 
    81657, 81658, 81659, 81660, 81661, 
    81662, 85626, 85757, 85758, 85759, 
    85627, 85628, 85629, 85630, 85631, 
    85632, 85633, 85875, 85874, 85873, 
    85872, 85876, 85877, 85878, 85879, 
    85880, 85881, 85882, 85864, 85865, 
    85866, 85867, 85868, 85869, 85870, 
    85871, 86299, 86298, 86297, 86637, 
    86638, 86716, 86717, 86718, 86719, 
    86720, 86721, 86722, 86723, 86724, 
    71871, 71868, 71870, 71869, 87456, 
    87455
  )

Query time 0.00537

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 72,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (71637,71636,71635,71634,71633,71632,71638,74647,74648,75520,75519,79251,79252,80381,81655,81656,81657,81658,81659,81660,81661,81662,85626,85757,85758,85759,85627,85628,85629,85630,85631,85632,85633,85875,85874,85873,85872,85876,85877,85878,85879,85880,85881,85882,85864,85865,85866,85867,85868,85869,85870,85871,86299,86298,86297,86637,86638,86716,86717,86718,86719,86720,86721,86722,86723,86724,71871,71868,71870,71869,87456,87455)"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "pfvd.lang_code = 'vi'"
        }
      }
    ]
  }
}