Latency Heatmap

Written for the variant you picked above: Night

Build a latency heatmap card. Props: title, columns [{label, counts[] — requests per latency bucket, lowest first}], edges (bucket edges in ms, one more than the buckets, log-spaced), slo (a target in ms), and theme. Helpers (pure functions): log-spaced edges between two latencies; the latency at a percentile from a histogram, found by walking the cumulative counts and interpolating on the log scale inside the bucket where it crosses; the requests in a rectangle of columns and buckets (either corner order) with their share of all requests in those columns; and a 0–1 shade for a count on a log scale (log1p(v) / log1p(max)), so quiet cells still show. Header: the title, then a line with the day's total and its overall p50, p95 and p99 (from all columns merged). On the right, three toggle chips (aria-pressed) with line keys to show or hide each percentile line. Chart (SVG, 300px tall, width from a ResizeObserver): one rect per column and bucket with a 1px gap and 1.5px corners, filled from a five-step blue sequential ramp — the lowest step is barely off the card for empty cells — by mixing the two neighbouring steps in oklab (color-mix) at the cell's shade. A log y-axis labelled at 3, 10, 30… ms and 1 s, 3 s; time labels along the bottom about every eighth column. Percentile lines run through the column centres: p50 in the ink colour, p95 orange, p99 a dashed aqua, each labelled with its last value at the right edge. The target is a dashed red line labelled "Target 400 ms". Interaction: pointing at a cell outlines it and shows a tooltip ("14:30 · 160–230 ms", "1,284 requests · 9.8% of the slot"). Pressing and dragging selects a rectangle (dashed outline, faint fill); the footer reads the count, the time and latency ranges and the share of traffic in those columns, with a Clear button. The plot is focusable: arrows move a cell cursor, Shift + arrows extend a selection from where it started, Escape clears. The footer also shows the ramp from Fewer to More. Two themes, night and paper, each with its own ramp and line colours. Selected variant — Night (night): Palette for this theme (Night): --lh-card #121317; --lh-ink #f2f3f5; --lh-line rgba(255, 255, 255, 0.08); --lh-muted #9a9ca4; --lh-p50 #f2f3f5; --lh-p95 #ff9a5c; --lh-p99 #3fd6a0; --lh-r0 #1a1d24; --lh-r1 #184f95; --lh-r2 #2a78d6; --lh-r3 #5598e7; --lh-r4 #b9d6f7; --lh-sel #ffffff; --lh-slo #ff8a7a; --lh-tip #f2f3f5; --lh-tip-ink #0a0b0e. Treat these as the root colour tokens, one value per role, and name them to suit your code. Select it with the theme option set to "night". Keep every dimension, spacing value, state and motion from the brief unchanged, and keep text at 4.5:1 contrast or better on these surfaces. This selection takes precedence over references to other themes or options in the general brief. Implement this selected appearance; do not add a variant picker or alternative appearances unless requested. Implementation requirements: Use React and TypeScript. Keep the component self-contained, with uniquely scoped CSS and no animation libraries. Include required imports, styles and font setup in the result. Interaction: Point at a cell to read it; drag to select a region and count it; toggle the percentile lines. Keyboard: arrows move, Shift + arrows select, Escape clears. Motion: None beyond quick hover states — it's a reading tool. Accessibility: The plot is a labelled, focusable group whose label gives the total and overall percentiles; cells, selections and the region count are reachable by keyboard, and the count is in a polite live region. Percentile lines differ by dash and label as well as colour. Responsive behavior: The grid stretches to its container (down to 300px) and time labels thin out on narrow screens; the header wraps. Touch: Dragging a finger selects a region (the plot doesn't scroll the page while you do); tapping a cell reads it. Preserve keyboard access, visible focus and reduced-motion behavior. Keep fictional demo data and simulated service calls in a separate usage example; expose callbacks for real actions and recover from rejected requests. Keep usage-example links inside the demo: use local buttons or prevent navigation. Demonstration links must not navigate to Vitrine routes or open other pages; preserve real URL support in the reusable component itself. Verify the result at narrow and wide viewport sizes, with keyboard input and reduced motion enabled.

Notes

Interaction

Point at a cell to read it; drag to select a region and count it; toggle the percentile lines. Keyboard: arrows move, Shift + arrows select, Escape clears.

Motion

None beyond quick hover states — it's a reading tool.

Accessibility

The plot is a labelled, focusable group whose label gives the total and overall percentiles; cells, selections and the region count are reachable by keyboard, and the count is in a polite live region. Percentile lines differ by dash and label as well as colour.

Responsive

The grid stretches to its container (down to 300px) and time labels thin out on narrow screens; the header wraps.

On touch

Dragging a finger selects a region (the plot doesn't scroll the page while you do); tapping a cell reads it.