SELECT 
  p.product_id, 
  ifnull(
    count(dp.post_id), 
    0
  ) as discussion_amount_posts 
FROM 
  cscart_discussion 
  INNER JOIN cscart_products as p ON (
    cscart_discussion.object_id = p.product_id
  ) 
  INNER JOIN cscart_discussion_posts as dp ON (
    cscart_discussion.thread_id = dp.thread_id 
    AND cscart_discussion.object_type = 'P' 
    AND cscart_discussion.company_id = 1
  ) 
WHERE 
  dp.status = 'A' 
  and p.product_id in (
    4, 
    1, 
    5, 
    7, 
    8, 
    9, 
    10, 
    11, 
    12, 
    13, 
    14, 
    15, 
    16, 
    17, 
    18, 
    19, 
    20, 
    21, 
    22, 
    23, 
    24, 
    25, 
    26, 
    27, 
    28, 
    29, 
    30, 
    31, 
    32, 
    33, 
    34, 
    35, 
    36, 
    37, 
    38, 
    39, 
    40, 
    41, 
    42, 
    43, 
    44, 
    45, 
    46, 
    47, 
    48, 
    49, 
    50, 
    51, 
    52, 
    53, 
    54, 
    55, 
    56, 
    57, 
    58, 
    59, 
    60, 
    62, 
    63, 
    64, 
    65, 
    67, 
    68, 
    69, 
    70, 
    71, 
    72, 
    73, 
    74, 
    75, 
    76, 
    78, 
    79, 
    80, 
    81, 
    82, 
    83, 
    84, 
    85, 
    86, 
    87, 
    88, 
    89, 
    90, 
    91, 
    92, 
    93, 
    94, 
    95, 
    96, 
    97, 
    100, 
    101, 
    102, 
    103, 
    104, 
    105, 
    106, 
    107, 
    108, 
    109, 
    110, 
    111, 
    112, 
    113, 
    114, 
    115, 
    116, 
    117, 
    118, 
    119, 
    120, 
    121, 
    122, 
    123, 
    124, 
    125, 
    126, 
    127, 
    128, 
    129, 
    130, 
    131, 
    132, 
    133, 
    134, 
    135, 
    136, 
    137, 
    138, 
    139, 
    140, 
    141, 
    142, 
    143, 
    144, 
    145, 
    146, 
    147, 
    148, 
    149, 
    150, 
    151, 
    152, 
    153, 
    154, 
    155, 
    156, 
    157, 
    158, 
    159, 
    160, 
    161, 
    162, 
    163, 
    164, 
    165, 
    167, 
    168, 
    169, 
    170, 
    171, 
    172, 
    173, 
    174, 
    175, 
    176, 
    177, 
    178, 
    179, 
    180, 
    181, 
    182, 
    183, 
    184, 
    185, 
    186, 
    187, 
    188, 
    189, 
    190, 
    191, 
    192, 
    194, 
    195, 
    196, 
    197, 
    198, 
    199, 
    200, 
    201, 
    202
  ) 
GROUP BY 
  p.product_id

Query time 0.00245

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "p.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "dp",
              "access_type": "ALL",
              "possible_keys": ["thread_id", "thread_id_2"],
              "rows": 17,
              "filtered": 100,
              "attached_condition": "dp.`status` = 'A'"
            }
          },
          {
            "table": {
              "table_name": "cscart_discussion",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY", "object_id", "idx_company_id"],
              "key": "PRIMARY",
              "key_length": "3",
              "used_key_parts": ["thread_id"],
              "ref": ["n764025_kutubminar123.dp.thread_id"],
              "rows": 1,
              "filtered": 100,
              "attached_condition": "cscart_discussion.company_id = 1 and cscart_discussion.object_type = 'P'"
            }
          },
          {
            "table": {
              "table_name": "p",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY"],
              "key": "PRIMARY",
              "key_length": "3",
              "used_key_parts": ["product_id"],
              "ref": ["n764025_kutubminar123.cscart_discussion.object_id"],
              "rows": 1,
              "filtered": 100,
              "attached_condition": "p.product_id in (4,1,5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,62,63,64,65,67,68,69,70,71,72,73,74,75,76,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,194,195,196,197,198,199,200,201,202)",
              "using_index": true
            }
          }
        ]
      }
    }
  }
}

Result

product_id discussion_amount_posts
1 1
5 1
8 1
23 1
78 1
167 1
172 1