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 (
    71676, 71677, 71913, 71912, 72194, 72193, 
    72415, 72416, 73305, 73304, 73527, 
    73526, 75232, 77936, 77934, 77935, 
    77945, 77943, 77944, 84336, 84335, 
    84536, 84639, 84537, 84528, 84530, 
    84531, 84532, 84533, 84534, 84535, 
    84638
  )

Query time 0.01372

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": 32,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (71676,71677,71913,71912,72194,72193,72415,72416,73305,73304,73527,73526,75232,77936,77934,77935,77945,77943,77944,84336,84335,84536,84639,84537,84528,84530,84531,84532,84533,84534,84535,84638)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}