Labs

Run your own config dump, seed sweep and scale ladder

One command: dump the configuration, generate data from a seed, sweep 1x to 30x, write raw results; random lookups into 8 to 240 MB, five seeds.

Closed-loop vs. open-loop, and coordinated omission (45 minutes)

A server slows from 40 ms to 400 ms under a closed-loop and an open-loop client; then a one-second freeze measured with and without intended-time correction.

Kill a node and measure the recovery

Three instances behind a health-checked proxy; kill the primary under steady load, three times, against the hypothesis "below 1% errors within 10 s".

Mean, percentile averaging and fan-out in 20 lines (30 minutes)

One million latencies, 1% of them slow: the mean, the percentiles, an average of shard p99s, and a fan-out of 100 calls.

Wall time minus CPU time

10,000 small writes with an fsync after each: wall time against CPU time, then one flush per 100 writes; with fsync and with macOS F_FULLFSYNC.

Measure your noise floor and your winner's curse (45 minutes)

An A/A spread over 10 identical runs, a "tuning sweep" of 30 identical configurations, and a blocked against interleaved A/B under background load.

A micro-benchmark that disappears, and a sampling blind spot

A billion x*x computed and discarded, then summed; and a 2 ms sleep once a second profiled at 99 Hz and 999 Hz.

Differential profile of two builds

Profile a JSON-parse-and-insert loop before and after adding a lock, diff the profiles frame by frame, then repeat with one side under extra load.

Catch a benchmark that did no work (30 minutes)

A C loop that "writes" a value 100 million times, with the result unused and then observable, against the ceiling for durable writes.

Random split versus group split versus hash split

50,000 rows for 500 couriers with personal biases: a random split, GroupKFold by courier, and a hash split; then 10% more rows and how many test rows move.