MySQL Query - Alternation of WHERE IN

Question

I have a mySQL query which takes 3-4 minutes to be executed. It is a large database. This query uses WHERE IN to find the rows.. So, is there any alternate query/clause/statement for my this query? (shortened and formatted version below)

SELECT r.reg_id, r.first_name, r.last_name, r.email, r.country, e.headline, 
e.industry, pp.photo FROM basic_registration r LEFT JOIN exp_ind_reg e ON
e.reg_id=r.reg_id LEFT JOIN profile_photo pp ON pp.reg_id=r.reg_id WHERE r.reg_id IN
(23,228,497,593,761,1204,1491,1894,1895,2128,7,11,20,22,25,26,27,29,31,
32,33,34,37,41,45,47,50,52,53,54,55,62,63,69,75,79,80,82,85,87,88,89,93,96,99,
102,104,106,110,116,117,124,139,143,146,150,157,159,161,162,170,175,176,177,
181,183,197,210,213,215,217,220,226,227,233,240,250,252,255,262,263,268,274,280,
283,285,290,300,312,313,317,324,332,341,347,351,357,368,369,372,373,377,
381,383,398,408,414,416,418,419,422,432,441,446,450,451,453,463,466,469,473,486,511,
522,525,527,529,534,538,541,543,546,564,566,569,577,579,581,585,586,595,598,599,600,
606,611,613,614,621,640,649,654,656,660,667,668,674,682,686,689,693,699,705,720,
734,742,748,753,763,774,775,780,782,784,792,795,804,839,841,862,871,890,929,
930,943,951,965,994,1004,1017,1026,1034,1050,1051,1053,1054,1067,1082,1087,1109,
1119,1121,1124,1136,1147,1187,1197,1214,1224,1226,1230,1241,1255,1318,1323,1358,1361,
1383,1404,1415,1429,1440,1443,1452,1458,1473,1478,1484,1490,1496,1505,1508,1521,
1534,1544,1556,1575,1628,1640,1644,1660,1688,1725,1791,1802,1815,1819,1849,1850,1891,
1896,1897,1911,1917,1923,1924,1926,1927,1930,1956,1959,1961,1967,1983,2006,2016,
2028,2053,2059,2088,2089,2100,2136,2145,2164,2183,2190,2219,2243,2291,2301,2321,
2343,2345,2423,2438,2465,2478,2501,2507,2508,2551,2563,2572,2629,2636,2642,2650,
2670,2693,2695,2724,2732,2801,2803,2839,2847,2867,2899,3024,3061,3068,3071,3093,
3123,3126,3188,3240,3273,3307,3308,3332,3484,3493,3522,3552,3596,3632,3705,3769,
3845,3869,3966,3969,4046,4066,4074,4077,4108,4113,4140,4198,4213,4218,4266,4295,
4312,4345,4365,4369,4380,4425,4453,4485,4486,4488,4493,4494,4495,4500,4513,4515,
4517,4520,4533,4540,4542,4544,4548,4550,4551,4554,4555,4557,4566,4567,4568,
4570,4572,4575,4586,4587,4590,4593,4594,4595,4598,4599,4608,4640,4642,4647,4650,
4661,4664,4679,4681,4685,4686,4698,4707,4708,4709,4711,4712,4714,4715,4717,4719,
4720,4721,4722,4724,4725,4728,4729,4732,4734,4735,4736,4737,4739,4742,4744,4745,
4750,4752,4754,4755,4757,4759,4760,4761,4763,4764,4766,4768,4770,4772,4774,4776,
4777,4789,4790,4791,4793,4795,4796,4797,4799,4803,4804,4805,4806,4808,4809,4811,
4814,4815,4817,4818,4821,4825,4826,4828,4830,4831,4833,4835,4836,4837,4843,4844,
4847,4848,4852,4853,4854,4861,4865,4866,4871,4874,4875,4876,4879,4880,4886,4889,
4890,4891,4892,4893,4894,4896,4899,4900,4904,4908,4914,4915,4916,4917,4918,4922,
4925,4929,4930,4931,4932,4934,4935,4940,4943,4944,4945,4947,4948,4949,4952,4953,
4956,4961,4963,4964,4965,4973,4974,4976,4978,4980,4985,4988,4989,4990,4993,4996,
5001,5009,5014,5016,5017,5018,5019,5021,5023,5024,5025,5028,5032,5033,5041,5042,
5048,5055,5056,5058,5059,5062,5065,5066,5072,5073,5075,5078,5079,5083,5084,5085,
5086,5087,5088,5089,5090,5091,5092,5093,5094,5096,5103,5112,5115,5116,5117,5123,
5125,5126,5127,5128,5130,5131,5132,5133,5134,5137,5138,5139,5140,5141,5146,5148,
5150,5155,5156,5158,5161,5162,5163,5164,5166,5168,5172,5174,5176,5178,5179,5180,
5181,5183,5186,5191,5194,5199,5200,5201,5202,5206,5214,5215,5217,5218,5222,5225,
5226,5227,5235,5236,5237,5243,5245,5246,5248,5251,5252,5254,5255,5256,5257,
5259,5261,5262,5267,5270,5271,5275,5279,5281,5283,5284,5286,5288,5289,5292,5293,
5295,5307,5308,5310,5311,5313,5315,5321,5323,5324,5325,5327,5328,5339,5340,5345,
5351,5353,5355,5356,5357,5358,5359,5363,5364,5365,5366,5369,5370,5371,5372,5373,
5376,5377,5378,5379,5381,5382,5383,5384,5385,5386,5387,5388,5389,5390,5393,5395,
5405,5406,5407,5411,5413,5414,5415,5416,5417,5418,5420,5424,5425,5429,5430,5431,
5432,5433,5434,5435,5437,5441,5451,5460,5467,5473,5476,5506,5524,5528,5530,5534,
5535,5536,5550,5551,5552,5553,5554,5556,5557,5559,5564,5565,5567,5568,5574,5575,
5585,5586,5587,5597,5600,5601,5605,5606,5607,5613,5614,5615,5617,5618,5624,5626,
5627,5628,5640,5643,5644,5645,5647,5648,5649,5650,5660,5661,5670,5671,5673,5674,
5675,5681,5683,5685,5689,5690,5691,5692,5693,5694,5695,5696,5697,5702,5703,5704,
5705,5706,5708,5710,5711,5712,5713,5716,5717,5719,5730,5732,5737,5744,5745,5746,
5748,5749,5750,5752,5753,5754,5756,5757,5758,5759,5761,5762,5763,5764,5765,5767,
5769,5770,5776,5780,5782,5783,5784,5787,5788,5789,5790,5791,5792,5793,5794,5799,
5802,5803,5804,5805,5806,5808,5809,5810,5812,5813,5814,5816,5817,5818,5822,5823,5826,
5827,5829,5830,5831,5848,5849,5850,5851,5852,5854,5856,5858,5859,5863,5864,5865,
5866,5867,5873,5884,5885,5893,5898,5899,5904,5907,5908,5910,5911,5915,5916,5918,
5919,5922,5923,5924,5933,5934,5941,5944,5950,5954,5955,5956,5960,5961,5973,5978,5981,
5982,5983,5984,5985,5986,5987,5988,5989,5990,5998,5999,6000,6002,6003,6004,6006,
6007,6010,6093,6175,6177,6217,6236,6325,6327,6347,6398,6403,6447,6582,6586,6609,
6697,6904,6926,6933,7001,7003,7047,7081,7094,7111,7205,7207,7219,7220,7221,7222,
7224,7227,7228,7229,7230,7232,7237,7238,7241,7268,7274,7275,7276,7281,7300,7307,
7309,7315,7330,7333,7334,7339,7343,7348,7354,7360,7374,7377,7378,7390,7429,7434,
7445,7448,7449,7452,7532,7534,7539,7542,7546,7547,7555,7563,7565,7567,7572,7575,
7576,7577,7578,7579,7585,7611,7907,7926,8100,8134,8205,8324,8337,8339,8350,8351,
8362,8410,8568,8572,8618,8619,8651,8665,8666,8667,8668,9010,9068,9098,9100,9106,
9111,9115,9121,9123,9174,9177,9272,9302,9421,9570,9683,9684,9697,9704,9712,9715,9779,
9790,9792,9793,9795,9798,9814,9818,9856,9866,9876,9886,9891,9908,9912,9928,10508,
10825,11103,11729,12289,12377,12643,12656,12657,12668,12876,12926,12958,13291,
13300,13408,13472,13976,14477,14538,14833,15044,15108,15779,16039,16061,16549,
16556,16562,16564,16565,16571,16573,16574,16576,16577,16584,16589,16590,16591,
16592,16598,16604,16606,16607,16610,16620,16645,16648,16650,16654,16655,16661,
16662,16675,16680,16697,16699,16701,16702,16704,16705,16708,16714,16719,16723,
16724,16727,16729,16731,16732,16743,16750,16752,16755,16758,16772,16774,16782,16787,
16793,16794,16795,16797,16798,16802,16813,16814,16815,16824,16825,16829,16831,
16841,16843,16848,16850,16863,16864,16866,16870,16878,16881,16887,16893,16896,16897,
16900,16902,16909,16912,16936,16944,16948,16958,16960,16963,16974,16978,16993,17012,
17016,17020,17053,17061,17096,17120,17124,17125,17129,17135,17137,17140,17141,17142,
17145,17149,17150,17157,17164,17170,17172,17173,17178,17180,17184,17187,17188,
17192,17196,17197,17200,17201,17206,17207,17221,17223,17227,17236,17244,17246,
17273,17285,17289,17291,17297,17300,17305,17310,17311,17321,17326,17331,17335,
17352,17370,17414,17423,17424,17439,17479,17493,17495,17501,17519,17525,17541,
17571,17590,17614,17755,17838,17846,17848,17852,17853,17855,17858,17861,17871,
17876,17877,17891,17896,17899,17900,17905,17908,17910,17911,17916,17917,17938,17939,
17940,17949,17953,17955,17960,17972,17980,17982,17992,18055,18067,18069,18071,18077,
18108,18127,18134,18136,18140,18142,18143,18158,18162,18178,18192,18196,18206,18217,
18221,18242,18245,18249,18263,18271,18273,18275,18277,18278,18286,18291,18295,18300,
18301,18308,18325,18333,18338,18360,18373,18374,18387,18397,18411,18412,18420,18429,
18434,18455,18478,18484,18534,18779,18790,18804,18821,18851,18964,18965,18977,18990,
18991,19000,19006,19276,19291,19374,19395,19416,19432,19627,19917,19927,19971,19974,
19989,20007,2254,2549,2652,3077,3615,4483,4484,4611,4700,5714,5772,6252,6536,7051,
7102,7107,7591,8167,8286,8935,9937,11089,12344,15830,16343,16644,17359,
17994,18774)
AND r.activation=1 ORDER BY r.first_name ASC LIMIT 0, 10;

or shortened version:

SELECT r.reg_id, r.first_name, r.last_name, r.email, r.country, 
       e.headline, e.industry, pp.photo 
FROM basic_registration r 
LEFT JOIN exp_ind_reg e ON e.reg_id=r.reg_id 
LEFT JOIN profile_photo pp ON pp.reg_id=r.reg_id 
WHERE r.reg_id IN (23,228,497,593,761,1204,1491,1894,1895,2128,)
      AND r.activation=1 
ORDER BY r.first_name ASC 
LIMIT 0, 10;

Explain is here

id  select_type     table   type    possible_keys   key     key_len     ref     rows    Extra
1    SIMPLE             r    range   PRIMARY    PRIMARY       8      NULL       1411    Using where; Using temporary; Using filesort
1    SIMPLE             e    ALL     NULL       NULL          NULL   NULL       667      
1    SIMPLE             pp   ref     reg_id     reg_id        8      linke4_linked_2.r.reg_id   1    

Answer 1

1. How do you know it's WHERE IN makes this query slow?
2. Why not to run this query with EXPLAIN keyword perpended and see what does it say? (single id in the IN clause for that purpose would be enough)
3. Armed with EXPLAIN results, you can do real optimisations on this query. Or ask here in SO for them