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, 73999, 73998, 74000, 73997, 
    74002, 74001, 74003, 74600, 74602, 
    75765, 75763, 75764, 75766, 79019, 
    79018, 81657, 81658, 81659, 81663, 
    81664, 81665, 81666, 81667, 81668, 
    81672, 81673, 81910, 81913, 81914, 
    81915, 81916, 81911, 81912, 85255, 
    85256, 85257, 85738, 85746, 85747, 
    85748, 85739, 85740, 85741, 85742, 
    85743, 85744, 85745, 85626, 85757, 
    85758, 85759, 85627, 85628, 85629, 
    85630, 85631, 85632, 85633, 86606, 
    86607, 86608, 71871, 71868, 71870, 
    71869
  )

Query time 0.00367

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 (71637,71636,71635,71634,71633,71632,71638,73999,73998,74000,73997,74002,74001,74003,74600,74602,75765,75763,75764,75766,79019,79018,81657,81658,81659,81663,81664,81665,81666,81667,81668,81672,81673,81910,81913,81914,81915,81916,81911,81912,85255,85256,85257,85738,85746,85747,85748,85739,85740,85741,85742,85743,85744,85745,85626,85757,85758,85759,85627,85628,85629,85630,85631,85632,85633,86606,86607,86608,71871,71868,71870,71869)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}