SELECT 
  * 
FROM 
  cscart_product_feature_variants 
WHERE 
  variant_id IN (
    2526, 1892, 1855, 1930, 617, 75, 474, 
    654, 47, 613, 837, 1699, 633, 125, 50, 
    1765, 540, 636, 604, 49, 612, 890, 602, 
    600, 601, 59, 611, 48, 422, 1354, 905, 
    64, 58, 473, 2982, 1856, 1870, 0, 2986, 
    590, 91, 2987
  )

Query time 0.00057

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": 42,
          "filtered": 100,
          "index_condition": "cscart_product_feature_variants.variant_id in (2526,1892,1855,1930,617,75,474,654,47,613,837,1699,633,125,50,1765,540,636,604,49,612,890,602,600,601,59,611,48,422,1354,905,64,58,473,2982,1856,1870,0,2986,590,91,2987)"
        }
      }
    ]
  }
}