SELECT 
  * 
FROM 
  cscart_product_feature_variants 
WHERE 
  variant_id IN (
    4786, 1895, 3095, 3097, 3096, 3099, 3100, 
    3101, 3102, 3103, 3085, 3686, 3087, 
    3089, 3092, 3090, 3093, 3094, 3104, 
    3084, 1859, 1870, 0, 1860, 1899, 1898, 
    1931, 1881, 1897
  )

Query time 0.00053

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 (4786,1895,3095,3097,3096,3099,3100,3101,3102,3103,3085,3686,3087,3089,3092,3090,3093,3094,3104,3084,1859,1870,0,1860,1899,1898,1931,1881,1897)"
        }
      }
    ]
  }
}