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Class Dashboard Load Estimator

Run the Class Dashboard Load Estimator Fullscreen

About This MicroSim

An LRS-Lite teacher dashboard has no dashboard server. The teacher's browser fetches every student's summary.json from object storage in parallel and computes the class heatmap, completion funnel and at-risk list itself. That works well for one class, but the download grows with the roster. The design estimates about 11 KB gzipped per student summary, puts 150 students at about one to four seconds, and adds an on-demand rollup function above roughly 100 students that pre-aggregates the class into one file.

This estimator does the arithmetic:

  • Total download (MB) = students × summary size (KB) ÷ 1000, fetched as one file per student.
  • The dashed line marks the total download at 100 students for the current summary size, the design's approximate threshold for using the rollup.
  • The thin gray bar is the rollup download: one file. Its size is an illustrative assumption (2 KB per student plus 20 KB of class aggregates), not a design figure.
  • The load-time band is an illustrative model calibrated so that 150 students at 11 KB gives about one to four seconds, as the design states.

The text panel names one of three outcomes: Browser aggregation is comfortable, Expect a few seconds, or Use the rollup function.

Learning objective: The learner will calculate the download size and load-time band for a teacher dashboard at a given roster size and decide whether the design's rollup function is needed.

Bloom's taxonomy level: Apply (verb: calculate)

How to Use

  1. At the defaults (30 students, 11 KB), read the panel: 30 downloads, 0.33 MB in total.
  2. Hover each bar to see its exact value and the formula behind it.
  3. Drag Students upward. Watch the total bar approach the dashed 100-student line, and note when the message changes.
  4. Drag Summary size up to 30 KB. The dashed line moves because it marks 100 students at the new size. Does a larger summary change when you should expect a few seconds?
  5. Set 150 students and 11 KB and check that the band matches the design's one to four seconds.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

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<iframe src="https://dmccreary.github.io/microsims/sims/class-dashboard-load-estimator/main.html"
        height="542px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Audience

Teachers, instructional designers, learning-technology developers and learning-analytics practitioners (college undergraduate and professional development).

Duration

10-15 minutes

Prerequisites

  • The idea of a browser-side dashboard and object storage sync (Chapter 23)
  • Kilobytes and megabytes (1 MB = 1000 KB in this model)

Activities

  1. Compute by hand (3 min): For 30, 90 and 150 students at 11 KB, compute the total download. Check each against the chart.
  2. Find the switch points (4 min): At 11 KB, find the smallest roster where the message becomes "Expect a few seconds" and where it becomes "Use the rollup function".
  3. Vary the summary (4 min): Repeat at 20 KB and 30 KB. Explain why the first switch point moves but the rollup threshold does not.
  4. Decide (3 min): A teacher has four sections of 35 students and wants one dashboard for all of them. Recommend whether to enable the rollup, citing the numbers.

Assessment

  • The learner computes the total download for a given roster and summary size.
  • The learner states the load-time band and which message applies, with a reason.
  • The learner explains which figures are design estimates and which are illustrative.

References

  1. Dashboard (computing) - Wikipedia. What a dashboard aggregates and displays.
  2. Amazon S3 - Wikipedia. The object store that holds each student's summary.json in the LRS-Lite design.
  3. Experience API - Wikipedia. The statement format summarized in each student's record.
  4. Chart.js bar chart documentation - Chart.js. The library used to draw the chart.