notes

About

Hemant Pandey — Systems Engineer Experience, projects, and résumé. MSCS at Georgia Tech.

A History of Software — new edition Hamming, Chapter 4. A 16-slide presentation with staged reveals, presenter notes, and a print layout.
The Art of Doing Science and Engineering — A History of Software Chapter 4. A 16-slide reading and discussion of software, abstraction, and discovery.

Before a function has an address Dynamic linking from ELF bytes to VMAs, PLT/GOT, dlsym, preload wrappers, and runtime patching. Includes a reproducible C lab.

01 Move the observer The big idea: a BPF runtime inside the application, with a loader, shared state, an agent, and a hook.
02 Follow the detour Step through Frida-Gum interception, BPF execution, native helpers, and return. Then follow the zpoline syscall route.
03 Before the first probe Agent startup, process boundaries, and a downloadable lab: install, attach, and run an entry/return counter.

The morning archive Dated explainers, worked examples, and questions to return to.

Reservoir computing: let the system move, learn how to read it A 9-minute guide to fading memory, nonlinear features, and training only the readout. Includes a live experiment.

Who owns a QUIC connection? A five-minute mental model for QUIC through firewalls, NAT, CGNAT, connection IDs, and migration.
BBR: how fast is the path, really? One path, two measurements, and the cost of probing. An argument for BBR, with interactive examples and contrasts with Reno, Copa, and CoDel.

From One Bit to a Queue Lecture 6 recap: TAS, cache-local spinning, backoff, ticket and array locks, NUMA locality, and the MCS queue lock.

01 The GIL is Not Your Enemy Refcounting, the 5ms handoff, and what the lock actually protects.
02 The Loop is the Trick epoll, coroutines, _run_once, and the Task spine that drives them.
03 Asyncio Sidequests The self-pipe, signals, debug mode, asyncio.run, contextvars, uvloop.
04 The Two-Way Door Generators, send, throw, yield from, and what await desugars to.
05 Scopes and Checkpoints anyio 101 — cancel scopes, checkpoints, task groups, memory streams.
06 Two Ways to Cancel The pre-armed peek and the task group that quietly turns it into a lie.
07 Servers, in Earnest Putting the loop to work behind a real request-serving stack.

Measure the Loop, Not the Request Instrumenting asyncio: stall canary, task census, py-spy, the five metrics.
Middleware is an Onion Starlette's request stack, layer by layer, and where it leaks.
The Peek That Always Returns False Chasing SSE disconnect detection through five middleware layers.
One Loop, Twenty Milliseconds How Pipecat moves real-time audio through a dozen AI services on a single event loop — without ever blocking.
An Hour on One Loop Architecting a voice agent on Temporal: a single activity that holds an asyncio loop open for half an hour, with WebRTC and Redis bridged in.

01 Motion is the Message Prediction, residue, quantization, entropy, and why AV1 is still built around guesses plus mistakes.

01 Fourier: When Waves Are The Right Coordinates Signals as mixtures of waves, filtering as coordinate selection, and the first transform-view habit.