SELECT 
  * 
FROM 
  cscart_product_feature_variants 
WHERE 
  variant_id IN (
    1855, 1930, 1831, 47, 135, 58, 1351, 605, 
    125, 473, 474, 59, 123, 654, 1832, 422, 
    64, 129, 88, 50, 1856, 1870, 0, 1, 637, 
    590, 341, 1808, 121
  )

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_feature_variants",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 29,
          "filtered": 100,
          "index_condition": "cscart_product_feature_variants.variant_id in (1855,1930,1831,47,135,58,1351,605,125,473,474,59,123,654,1832,422,64,129,88,50,1856,1870,0,1,637,590,341,1808,121)"
        }
      }
    ]
  }
}