a migration role, not a migration window
Moving live state between two foundations is the part of distributed design that usually happens once, badly, at an unsociable hour. This record treats it as a standing role instead of an incident.
field notes
Writing
Short notes from real engineering work: one decision, one incident, one reversal at a time. Each one names the shape of the problem, the tension that made it hard, the decision, and what it cost. The internals stay out — the codename is the hint.
If you have five minutes rather than an afternoon: the three case studies condense this material to one problem, one decision and what the decision cost. The notes below are the record those studies cite — and the projects the codenames belong to are on the front page.
All field notes
all
ABACUS 60
FLINT 12
KEEL 24
LARDER 24
LATTICE 36
MERIDIAN 24
MISE 24
SCRIBE 12
TROUPE 12
UMBRA 24
theme: migration · 244 total
every layer that was supposed to be transparent
The first service migration looked like a copy and a connection string: take a database out of the application's container, run it as a supervised process on the host, point the application at it. The move took far longer than that, and…
method
What a field note is
Not a changelog entry and not a repository summary. One decision, one incident, one reversal, or one hard-won invariant — the thing an engineer would tell you at a whiteboard.
shape
What made the problem genuinely hard, before any solution appeared.
tension
The two things that could not both be true — stated precisely, because
that is the part that transfers.
decision
What was chosen, and what it cost. Cost is the
credibility; a decision with no cost attached has not been described.
ceiling
A codename, a theme, and a class of problem — never a hostname, a
parameter, a version or a vendor. Under the disclosure rules the hint
is the category, not the instance.
Prefer records with dates and root causes? Those are on incidents. Live numbers are on stats.