Notes

Browse by topic

Three topic hubs; each one defines the area, offers a start path, and lists the notes.

Start here (reading paths)

Three short reading paths, one per topic.

Performance

1. TTFB and origin latencyUnderstand request phases and what “first byte” really contains.
2. Queueing basics and latency budgetsWhy tail latency explodes and how to set budgets that survive load.
3. Performance regressions checklistA workflow to confirm, isolate, and mitigate regressions.

Formal methods

1. Specs, invariants, and contractsWrite constraints you can review, test, and monitor.
2. Model checking primerExplore behaviour spaces and interpret counterexamples.
3. Session types and protocolsMake interaction structure explicit and checkable.

Distributed systems

1. Time, clocks, and orderingDefine “before” without relying on a single clock.
2. Failure modes, retries, idempotencyDesign operations so retry behaviour is safe and predictable.
3. Observability for distributed systemsDebug with evidence across service boundaries.

Latest notes

Six recent notes across all topics.

• Observability for distributed systemsHow traces and correlation IDs turn incidents into evidence. distributed
• Performance regressions checklistA repeatable workflow for confirming and localising regressions. performance
• Specs, invariants, and contractsWhat to write down so behaviour stays reviewable. formal
• Failure modes, retries, and idempotencyWhy retries create duplicates and how to make outcomes safe. distributed
• Cache hierarchy: edge to originReason about caches as a system, not a single knob. performance
• Behavioural equivalence in plain EnglishWhat “same behaviour” means depends on your observations. formal

How notes are written

• Quick summaryA short statement of what the note covers and why it matters.
• Key ideasDefinitions and mini examples to build working intuition.
• Common pitfallsThe mistakes that recur in practice (measurement, assumptions, and semantics).
• Related notesInternal links that keep the knowledge base navigable and crawlable.