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 (
    69670, 69671, 71958, 71957, 71956, 72039, 
    72038, 72040, 72067, 72068, 72073, 
    72072, 72074, 72161, 72162, 75740, 
    75739, 75747, 75749, 75748, 75787, 
    75786, 80876, 80878, 80879, 80880, 
    80881, 80877, 80915, 80916, 75781, 
    81344, 81345, 75782, 81440, 81445, 
    81446, 81447, 81441, 81442, 81443, 
    81444, 81927, 81928, 81929
  )

Query time 0.00382

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": 45,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (69670,69671,71958,71957,71956,72039,72038,72040,72067,72068,72073,72072,72074,72161,72162,75740,75739,75747,75749,75748,75787,75786,80876,80878,80879,80880,80881,80877,80915,80916,75781,81344,81345,75782,81440,81445,81446,81447,81441,81442,81443,81444,81927,81928,81929)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}