HARUMI
01PORTFOLIO

Harumi Morikawa

Platform / Backend Engineer · Based in Japan

I run the systems I write about.

Listing what I know is inventory. Showing what I measured — and what I got wrong — is evidence. Only one of those is hard to copy, so this site keeps the second kind: the numbers behind each decision, the fixes I removed rather than defended, and the procedure I wrote one morning and skipped that same afternoon.

Read the three casesHow I work

Selected work below

  • 01Running systems, not portfolio props
  • 02Every claim tied to evidence
  • 03Public products separated from lab notes

02How I work

Observe, Plan, change, prove, retain, and observe again. One loop underneath every project here — distilled from operating this lab, including the parts that went wrong.

  1. 01 / OBSERVE

    Check the real state

  2. 02 / PLAN

    Define the finish before changing anything

  3. 03 / CHANGE

    Change one authority, with its guard

  4. 04 / PROVE

    Prove the exact change in production

  5. 05 / RETAIN

    Turn the result into the next input

  6. 06 / RE-OBSERVE

    Sample the real state again

A check that has only ever printed green has not proved anything.

A status condition reports what a controller last did, not the property you care about.

Record the diagnosis before you implement it — a session can end before its work does.

Read the full loop →See the architecture →

03Three cases

Chosen for what they prove, not for scale. Each carries one claim, the evidence behind it, and the decision that followed.

01

Camunda upgrade

Connection policy: measure before tuning
Claim
A fix that appears to work can be the thing making it worse. The only way to tell is to measure it.
Evidence
Envoy’s own /clusters stats: the “fixed” service opened 697 connections to serve 778 requests. A comparable service left out of the change reused them normally — 88 for 182.
Decision
Removed outright rather than re-tuned, with the reasoning written down so it cannot quietly return.
Read the write-up →

02

Harumi Platform

GitOps delivery with runtime proof
Claim
Push to main is the deploy. Applications register themselves from their own repositories, and retire the same way.
Evidence
Two guardrails reported green because neither could ever go red: a validator that never resolved the very import that was broken, and a deploy check watching a pipeline an automated commit had already replaced.
Decision
Before trusting “nothing found”, make the same probe return something first — a check that could not run looks exactly like one that passed.
Read the write-up →

03

NOEMA

Private recovery without operator overrideRetired 2026-10 - the service is no longer running; this page records the design.
Claim
A private journal is only private if the identity model holds. Recovery is where that model usually breaks.
Evidence
No email reset path means a forgotten password destroys the most private data permanently — but the usual reset flow makes recovery the easiest way into exactly what the system protects.
Decision
Recovery rests on a second secret the person writes themselves. The answer exists only as a hash — no operator can restore an account, including me.
Read the write-up →

04In the open

Public product notes, with clear access boundaries.

LIVE · PERSONAL PRODUCT

One event layer for every notification.

MakeUp is a relationship app for any close pair, with shared calendars, moods, apologies and nudges. Every feature publishes to one event topic, so persistence, live updates and Web Push come with it.

  • One Kafka topic, one consumer
  • SSE and Web Push from one event
  • Chinese, Japanese and English UI
Open MakeUp ↗

INVITATION ONLY · LEARNING PLATFORM

Read, learn, return daily.

LexTrace is an invitation-only learning platform with repository reading, a vocabulary track and an IPA Fundamental Information Technology Engineer syllabus path with quick-scan mode. Passkey sign-in and a daily review calendar support returning to study.

  • Repository reading and vocabulary
  • IPA syllabus with quick-scan mode
  • Passkey sign-in and daily review
  • Verified 9 Oct 2026
Open LexTrace ↗

05Open source

Code I publish, so the claims can be checked.

06Live

A claim that verifies itself, continuously.

05bare-metal nodes04public applications04selected systems01GitOps delivery path

07Everything else

Reachable, not merchandised.

All projects and milestones →

08ABOUT

Based in Japan

中文 · 日本語 · English

Platform / Backend Engineer

Verify the source of truth.

Remove, don’t layer.

Ship, listen, revert honestly.

Full profile →