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 = 'en' 
WHERE 
  pfv.variant_id IN (
    70183, 70182, 70181, 70180, 70179, 70178, 
    70177, 70176, 70239, 70238, 70237, 
    70236, 70235, 70234, 70233, 70249, 
    70248, 70247, 70246, 70245, 70244, 
    70243, 70242, 70241, 70250, 74592, 
    74591, 74593, 74595, 74594, 74596
  )

Query time 0.00630

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": 31,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70183,70182,70181,70180,70179,70178,70177,70176,70239,70238,70237,70236,70235,70234,70233,70249,70248,70247,70246,70245,70244,70243,70242,70241,70250,74592,74591,74593,74595,74594,74596)"
        }
      },
      {
        "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 = 'en'"
        }
      }
    ]
  }
}