How it’s built
Patterns behind the tools
Each tool here is deliberately built on a named enterprise software pattern, and doubles as a public, working demo of it. These are the write-ups.
State machine
read itPomodoro Timer
A finite state machine on the server: explicit states, named transitions, invalid moves rejected at the domain layer, one active session enforced by the database.
Event sourcing + CQRS
read itGTD Task Manager
Each task is an append-only event stream; the aggregate is rebuilt by replay and validates commands against that state. A projection maintains the query-optimized board in the same transaction.
Task & Work archetype
write-up soonHabit Tracker
A habit is an ActivityPlan; each check-off is an instance in an append-only log. Streaks are a pure function of the log and the frequency rule.
Accounting archetype
read itBudget Tracker
An envelope is an account; every expense is an immutable entry in an append-only ledger. Spent and remaining are always derived by summing entries — never stored — and corrections are reversal entries, not deletes.