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 (
    70932, 70931, 70933, 70935, 70934, 70936, 
    70938, 70937, 70939, 70941, 70940, 
    70942, 70944, 70943, 70945, 70947, 
    70946, 70948, 70950, 70949, 70951, 
    70953, 70952, 70954, 70956, 70955, 
    70957, 70959, 70958, 70960, 70962, 
    70961, 70963, 70965, 70964, 70966, 
    70968, 70967, 70969, 70971, 70970, 
    70972, 70974, 70973, 70975, 70977, 
    70976, 70978, 70980, 70979, 70981, 
    70983, 70982, 70984, 70986, 70985, 
    70987, 70989, 70988, 70990
  )

Query time 0.00506

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": 60,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70932,70931,70933,70935,70934,70936,70938,70937,70939,70941,70940,70942,70944,70943,70945,70947,70946,70948,70950,70949,70951,70953,70952,70954,70956,70955,70957,70959,70958,70960,70962,70961,70963,70965,70964,70966,70968,70967,70969,70971,70970,70972,70974,70973,70975,70977,70976,70978,70980,70979,70981,70983,70982,70984,70986,70985,70987,70989,70988,70990)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}