Hit counter: fix the five-minute window, keep it fast all day, then add shorter windows

Context

Welcome to the news analytics team. hits/ counts how often each story on the market news feed is opened; the rules are in README.md. Three items are open: a wrong count at the edge of the window, a counter that slows down as the day goes on, and a new query the panel needs.

You have 35 minutes. The checks are graded one by one, so each part you get working counts even if the rest is not done.

HC-1: Hits stay in the window one second too long

Report

A story opened once at second 1 still shows one view at second 301, a full five minutes later.

Acceptance criteria

• A hit at t is counted up to t + 299 and not at t + 300.

HC-2: The counter slows down all day

Report

By the afternoon, each count on a busy story takes longer than the one before, and the panel times out.

Acceptance criteria

• hit and count stay fast however long the counter runs and however many hits arrive in one second.
• What count returns does not change.

HC-3: Shorter windows (level 3)

Acceptance criteria

• count_since(timestamp, seconds) counts the hits in the last seconds seconds, as the README describes.
• seconds above 300 counts the whole window; seconds of 0 or less gives 0.

Notes

• Run pytest tests/visible. Four tests fail on the current code.
• The hidden checks include a full day of traffic, with a time limit.
• Practice task modelled on a candidate's report of Bloomberg's new-grad software engineering interviews, where one round was a hit counter with follow-ups on time and memory. Original StackYard code, not the actual question; not affiliated with Bloomberg.