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 (
    68417, 68418, 69835, 69836, 69845, 69844, 
    69843, 69842, 69846, 71079, 71080, 
    77372, 79256, 79255, 79266, 79265, 
    81991, 81992, 81993, 82357, 82358, 
    84675, 84674, 84673, 84672, 84671, 
    84670, 84676, 84677, 84701, 84702, 
    84703, 84704, 84705, 84708, 84709, 
    84710, 84711, 84712, 84713, 84714, 
    84715, 85471, 85472, 85473, 85610, 
    85611, 85612
  )

Query time 0.00631

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": 48,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68417,68418,69835,69836,69845,69844,69843,69842,69846,71079,71080,77372,79256,79255,79266,79265,81991,81992,81993,82357,82358,84675,84674,84673,84672,84671,84670,84676,84677,84701,84702,84703,84704,84705,84708,84709,84710,84711,84712,84713,84714,84715,85471,85472,85473,85610,85611,85612)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}