SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (52, 33, 53, 45)

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_variation_group_products",
      "access_type": "range",
      "possible_keys": ["idx_group_id"],
      "key": "idx_group_id",
      "key_length": "3",
      "used_key_parts": ["group_id"],
      "rows": 19,
      "filtered": 100,
      "index_condition": "cscart_product_variation_group_products.group_id in (52,33,53,45)"
    }
  }
}

Result

product_id group_id
220 33
219 33
134 33
221 33
222 33
223 33
261 45
260 45
137 45
262 45
263 45
264 45
132 52
283 52
284 52
127 53
285 53
286 53