letloop — HTTP server benchmark report

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Fastest

C (h2o)

504,899 req/s (libh2o-evloop)

Runner-up

letloop

448,768 req/s (pico + io_uring)

Lowest p99

letloop

0.008ms

Implementations

languages tested

Peak throughput rankings

#	Language	Framework	Peak req/s	@ conns	Avg (ms)	p99 (ms)
1	C (h2o)	libh2o-evloop	504,899	256	0.485	0.88
2	letloop	pico + io_uring	448,768	64	0.137	0.159
3	Rust	axum + tokio	410,948	8	0.019	0.021
4	Java (Vert.x)	Vert.x	362,643	4	0.069	2.22
5	Bun (canary)	Bun.serve() (canary, Rust)	316,374	64	0.215	0.299
6	Bun	Bun.serve()	302,272	8	0.029	0.106
7	Deno	Deno.serve()	264,358	8	0.029	0.036
8	Go	net/http (stdlib)	224,278	8	0.037	0.090
9	Node.js	http (stdlib)	192,824	4	0.027	0.052
10	Java (Loom)	HttpServer + virtual threads	112,088	8	0.109	1.79
11	Gleam	mist + gleam_otp	111,925	4	0.040	0.047
12	Common Lisp	Hunchentoot	88,305	4	0.061	0.656
13	Racket	web-server (stdlib)	68,474	16	0.234	0.279
14	FastAPI	uvicorn	44,864	32	0.710	1.36
15	Ruby	Falcon (async)	41,952	16	0.378	0.608
16	Flask	gunicorn (1 worker)	12,397	1	0.083	0.107

Conns	Req/s	Avg (ms)	p99 (ms)
1	172,752	0.012	0.033
2	330,660	0.007	0.010
4	398,228	0.010	0.013
8	411,089	0.015	0.024
16	492,297	0.146	2.69
32	486,479	0.067	0.126
64	490,070	0.128	0.250
128	493,294	0.238	0.457
256	504,899	0.485	0.88

Conns	Req/s	Avg (ms)	p99 (ms)
1	163,988	0.006	0.008
2	326,854	0.007	0.009
4	401,648	0.009	0.012
8	422,523	0.016	0.020
16	446,988	0.037	0.047
32	448,392	0.069	0.090
64	448,768	0.137	0.159
128	429,720	0.270	0.433
256	396,001	0.588	0.843

Conns	Req/s	Avg (ms)	p99 (ms)
1	142,561	0.009	0.009
2	366,798	0.005	0.008
4	399,368	0.010	0.011
8	410,948	0.019	0.021
16	386,443	0.044	0.045
32	364,713	0.087	0.093
64	356,554	0.412	0.232
128	357,334	0.327	0.385
256	341,019	0.685	0.96

Conns	Req/s	Avg (ms)	p99 (ms)
1	134,461	0.035	1.19
2	328,274	0.063	2.22
4	362,643	0.069	2.22
8	360,192	0.095	2.47
16	353,607	0.104	2.25
32	351,927	0.152	2.43
64	348,055	0.257	2.77
128	339,698	0.422	3.20
256	331,354	0.793	4.09

Conns	Req/s	Avg (ms)	p99 (ms)
1	127,939	0.011	0.033
2	227,555	0.009	0.030
4	276,453	0.016	0.049
8	304,994	0.026	0.056
16	311,187	0.052	0.102
32	315,307	0.101	0.181
64	316,374	0.215	0.299
128	304,681	0.393	0.563
256	279,722	0.86	1.09

Conns	Req/s	Avg (ms)	p99 (ms)
1	120,344	0.013	0.063
2	252,272	0.013	0.089
4	291,298	0.015	0.075
8	302,272	0.029	0.106
16	295,739	0.060	0.195
32	295,356	0.109	0.226
64	293,695	0.225	0.370
128	286,612	0.443	0.637
256	280,967	0.86	1.19

Conns	Req/s	Avg (ms)	p99 (ms)
1	100,436	0.013	0.015
2	201,872	0.010	0.016
4	241,437	0.016	0.019
8	264,358	0.029	0.036
16	258,101	0.062	0.092
32	248,565	0.129	0.175
64	244,864	0.265	0.306
128	239,777	0.517	0.599
256	233,156	1.03	1.22

Conns	Req/s	Avg (ms)	p99 (ms)
1	105,340	0.019	0.114
2	213,846	0.010	0.030
4	222,673	0.020	0.057
8	224,278	0.037	0.090
16	215,993	0.078	0.177
32	213,764	0.150	0.317
64	207,669	0.315	0.655
128	201,046	0.585	1.25
256	190,086	1.25	2.17

Conns	Req/s	Avg (ms)	p99 (ms)
1	106,893	0.029	0.794
2	182,658	0.022	0.056
4	192,824	0.027	0.052
8	191,393	0.049	0.089
16	190,017	0.090	0.162
32	185,213	0.178	0.239
64	182,036	0.361	0.427
128	172,841	0.732	0.86
256	167,911	1.84	1.73

Conns	Req/s	Avg (ms)	p99 (ms)
1	84,387	0.059	1.82
2	96,575	0.051	1.34
4	106,732	0.066	1.29
8	112,088	0.109	1.79
16	110,510	0.184	2.03
32	110,808	0.336	2.55
64	110,624	0.638	3.10
128	107,113	1.14	3.63
256	94,478	3.36	6.98

Conns	Req/s	Avg (ms)	p99 (ms)
1	71,225	0.024	0.281
2	88,821	0.032	0.294
4	111,925	0.040	0.047
8	111,761	0.077	0.085
16	111,031	0.147	0.177
32	111,364	0.287	0.312
64	109,786	0.572	0.610
128	107,234	1.09	1.33
256	102,144	2.35	2.89

Conns	Req/s	Avg (ms)	p99 (ms)
1	64,151	0.038	0.95
2	83,844	0.044	0.764
4	88,305	0.061	0.656
8	87,096	0.110	0.799
16	87,334	0.193	0.596
32	86,044	0.385	1.05
64	83,876	0.799	2.51
128	79,019	1.61	6.91
256	74,224	6.17	57.53

Conns	Req/s	Avg (ms)	p99 (ms)
1	58,305	0.027	0.285
2	65,760	0.040	0.229
4	67,393	0.065	0.125
8	67,770	0.121	0.250
16	68,474	0.234	0.279
32	66,980	0.477	0.546
64	66,400	0.94	1.49
128	66,044	1.77	3.38
256	62,518	3.73	7.12

Conns	Req/s	Avg (ms)	p99 (ms)
1	34,919	0.031	0.041
2	41,431	0.051	0.079
4	40,756	0.106	0.443
8	42,352	0.188	0.252
16	43,858	0.364	0.608
32	44,864	0.710	1.36
64	44,140	1.46	2.43
128	44,556	2.85	5.07
256	43,156	8.70	140.71

Conns	Req/s	Avg (ms)	p99 (ms)
1	34,233	0.049	0.668
2	38,907	0.064	0.321
4	40,345	0.105	0.314
8	41,334	0.197	0.427
16	41,952	0.378	0.608
32	41,832	0.764	1.00
64	39,698	1.58	1.85
128	36,912	3.19	3.31
256	36,501	7.96	35.21

Conns	Req/s	Avg (ms)	p99 (ms)
1	12,397	0.083	0.107
2	11,959	0.172	0.408
4	12,019	0.335	0.468
8	11,982	0.669	1.08
16	12,113	1.32	1.50
32	11,941	2.68	2.98
64	11,407	5.52	6.12
128	10,565	11.02	12.38
256	9,710	23.99	26.92

Connections	1st	2nd	3rd	4th	5th
1	1C (h2o)172,752 req/s	2letloop163,988 req/s	3Rust142,561 req/s	4Java (Vert.x)134,461 req/s	5Bun (canary)127,939 req/s
2	1Rust366,798 req/s	2C (h2o)330,660 req/s	3Java (Vert.x)328,274 req/s	4letloop326,854 req/s	5Bun252,272 req/s
4	1letloop401,648 req/s	2Rust399,368 req/s	3C (h2o)398,228 req/s	4Java (Vert.x)362,643 req/s	5Bun291,298 req/s
8	1letloop422,523 req/s	2C (h2o)411,089 req/s	3Rust410,948 req/s	4Java (Vert.x)360,192 req/s	5Bun (canary)304,994 req/s
16	1C (h2o)492,297 req/s	2letloop446,988 req/s	3Rust386,443 req/s	4Java (Vert.x)353,607 req/s	5Bun (canary)311,187 req/s
32	1C (h2o)486,479 req/s	2letloop448,392 req/s	3Rust364,713 req/s	4Java (Vert.x)351,927 req/s	5Bun (canary)315,307 req/s
64	1C (h2o)490,070 req/s	2letloop448,768 req/s	3Rust356,554 req/s	4Java (Vert.x)348,055 req/s	5Bun (canary)316,374 req/s
128	1C (h2o)493,294 req/s	2letloop429,720 req/s	3Rust357,334 req/s	4Java (Vert.x)339,698 req/s	5Bun (canary)304,681 req/s
256	1C (h2o)504,899 req/s	2letloop396,001 req/s	3Rust341,019 req/s	4Java (Vert.x)331,354 req/s	5Bun280,967 req/s