The report page was slow.
Our most experienced engineer
took it,
and by lunch
he had a plan.
A cache in front of the query.
Invalidation on every write.
A background job
to warm it overnight.
It was a good plan.
He had built it
five times before,
and five times
it had worked.
The new joiner
read the ticket,
ran the query
with explain,
and asked
if anyone had tried
adding the missing index.
One line.
The page went
from nine seconds
to forty milliseconds.
Nobody had checked
the query plan
because the answer
had arrived before the question
had finished.
He was not careless.
He was experienced,
and that was the problem.
In 1942
Abraham Luchins
gave people puzzles
about measuring water with jars.
The first few
could only be solved
with one long sequence of pourings.
Then came puzzles
that had a much simpler answer.
Most of the people
who had practised the long method
kept using it.
People who started
straight on the later puzzles
mostly found the short way.
Some practised people
failed a puzzle
the long method could not solve,
even though the short one could.
It is called
the Einstellung effect.
A method that worked
becomes the way
you see the problem.
Decades later
the same was shown
in strong chess players.
A familiar winning pattern
on the board
kept them from finding
a shorter one,
and their eyes
kept going back to the familiar squares.
Experience
is not only knowing answers.
It is the first answer
arriving so fast
that the others never get a turn.
So when the solution
appears instantly,
treat that as a signal
to slow down,
not as proof.
Ask what you would try
if your usual tool
did not exist.
Say the problem out loud
without the solution in it.
And ask the newest person
how they would start.
Not to be polite.
Because they have not learned
what not to see.
– Serguey Asael Shinder
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