perf: small improvements in Synth

[meskill]

Summary:
Briefly describe the changes made in this PR.

Issue Reference(s):
Fixes #... (Replace "..." with the issue number)

Build & Testing:

• I ran cargo test successfully.
• I have run ./lint.sh --mode=fix to fix all linting issues raised by ./lint.sh --mode=check.

Checklist:

• I have added relevant unit & integration tests.
• I have updated the documentation accordingly.
• I have performed a self-review of my code.
• PR follows the naming convention of <type>(<optional scope>): <title>

[codecov]

Codecov Report

Attention: Patch coverage is 85.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 87.37%. Comparing base (3d330e1) to head (d8d5ef6).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/core/json/serde.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3051      +/-   ##
==========================================
- Coverage   87.39%   87.37%   -0.03%     
==========================================
  Files         275      275              
  Lines       27149    27165      +16     
==========================================
+ Hits        23728    23735       +7     
- Misses       3421     3430       +9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

Bencher Report

Branch	3051/merge
Testbed	benchmarking-runner

⚠️ WARNING: The following Measure does not have a Threshold. Without a Threshold, no Alerts will ever be generated!

• Latency

Click here to create a new Threshold
For more information, see the Threshold documentation.
To only post results if a Threshold exists, set the --ci-only-thresholds CLI flag.

Click to view all benchmark results

Benchmark	Latency	nanoseconds (ns)
from_json_bench	📈 view plot ⚠️ NO THRESHOLD	6,249,200.00
group_by	📈 view plot ⚠️ NO THRESHOLD	495.30
input/args.missing	📈 view plot ⚠️ NO THRESHOLD	22.84
input/args.nested.existing	📈 view plot ⚠️ NO THRESHOLD	43.17
input/args.nested.missing	📈 view plot ⚠️ NO THRESHOLD	38.51
input/args.root	📈 view plot ⚠️ NO THRESHOLD	38.80
input/headers.existing	📈 view plot ⚠️ NO THRESHOLD	32.63
input/headers.missing	📈 view plot ⚠️ NO THRESHOLD	31.82
input/value.missing	📈 view plot ⚠️ NO THRESHOLD	23.74
input/value.nested.existing	📈 view plot ⚠️ NO THRESHOLD	42.24
input/value.nested.missing	📈 view plot ⚠️ NO THRESHOLD	35.38
input/value.root	📈 view plot ⚠️ NO THRESHOLD	39.66
input/vars.existing	📈 view plot ⚠️ NO THRESHOLD	8.16
input/vars.missing	📈 view plot ⚠️ NO THRESHOLD	8.72
synth_nested	📈 view plot ⚠️ NO THRESHOLD	104,160.00
synth_nested_borrow	📈 view plot ⚠️ NO THRESHOLD	52,856.00
test_batched_body	📈 view plot ⚠️ NO THRESHOLD	1,915.40
test_batched_body #2	📈 view plot ⚠️ NO THRESHOLD	1,554,400.00
test_data_loader	📈 view plot ⚠️ NO THRESHOLD	391,540.00
test_handle_request	📈 view plot ⚠️ NO THRESHOLD	130,050.00
test_handle_request_jit	📈 view plot ⚠️ NO THRESHOLD	64,012.00
test_http_execute_method	📈 view plot ⚠️ NO THRESHOLD	15,374.00
with_mustache_expressions	📈 view plot ⚠️ NO THRESHOLD	1,136.00
with_mustache_literal	📈 view plot ⚠️ NO THRESHOLD	738.91

🐰 View full continuous benchmarking report in Bencher

[meskill]

RPS changes locally:

posts title

before

Running 30s test @ http://localhost:8000/graphql
  4 threads and 100 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     2.95ms   14.36ms 486.95ms   99.11%
    Req/Sec    13.96k     2.02k   18.78k    89.16%
  1670008 requests in 27.10s, 8.37GB read
  Socket errors: connect 0, read 0, write 0, timeout 100
Requests/sec:  61623.45
Transfer/sec:    316.29MB

after

Running 30s test @ http://localhost:8000/graphql
  4 threads and 100 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     2.89ms   15.14ms 551.80ms   99.09%
    Req/Sec    15.33k     2.66k   27.94k    85.63%
  1832428 requests in 27.66s, 9.18GB read
  Socket errors: connect 0, read 0, write 0, timeout 100
Requests/sec:  66243.75
Transfer/sec:    340.01MB

big query

before

Running 30s test @ http://localhost:8000/graphql
  4 threads and 100 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    10.03ms    4.46ms 117.46ms   85.96%
    Req/Sec     2.59k     0.87k   16.07k    93.05%
  304120 requests in 29.64s, 15.04GB read
  Socket errors: connect 0, read 0, write 0, timeout 100
Requests/sec:  10259.24
Transfer/sec:    519.61MB

after

Running 30s test @ http://localhost:8000/graphql
  4 threads and 100 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     9.26ms    3.05ms  68.16ms   75.51%
    Req/Sec     2.73k   236.40     3.05k    83.42%
  325544 requests in 30.05s, 16.10GB read
Requests/sec:  10832.93
Transfer/sec:    548.66MB