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 (
    69685, 69749, 69748, 69750, 70122, 70123, 
    70126, 70127, 70956, 70955, 70957, 
    70974, 70973, 70975, 70977, 70976, 
    70978, 71483, 71484, 74204, 74203, 
    76046, 78653, 78652, 78654, 79922, 
    79921, 79920, 80847, 82260, 82261, 
    82560, 82562, 82559, 82561
  )

Query time 0.00248

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": 35,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (69685,69749,69748,69750,70122,70123,70126,70127,70956,70955,70957,70974,70973,70975,70977,70976,70978,71483,71484,74204,74203,76046,78653,78652,78654,79922,79921,79920,80847,82260,82261,82560,82562,82559,82561)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}