[clinic · EX-21] Cost model for a real client shape

[akash-coded]

Exercise clinic. One long-running thread per exercise. Ask here rather than opening a
new thread — the answers accumulate where the next person will look for them.

Exercise: EX-21 — Cost model for a real client shape · difficulty 🟡

What this exercise asks

Read the exercise first; this thread is for when you are stuck, not instead of it.

Three ways people get stuck on this one

1. Modelling per-query cost only. The cluster, the initial backfill and the re-embed cycle are the majority — #44.

2. Assuming the corpus is static. The change rate drives the re-embed bill and is the input people never ask for.

3. One point estimate with no sensitivity. The useful output is which input moves the total most.

How to ask here

Post the numbers you got, the config that produced them, and what you already tried.
A question with a measurement in it gets answered in one round trip; a question without one
takes three.

If you have finished it, post the write-up in Show and Tell with the
[solution · EX-21] prefix rather than here — this thread stays for people who are stuck.