nate-gehringer

Some Musings on Guard Clauses and Fault Tolerance

“Or: How I Learned to Stop Worrying and Love the Exception”

Background

I used to work at a healthcare technology company that was headed on the tech side by a database nut. The data model was both sprawling and very normalized (by that, I mean gnarly). We worked mainly in the exciting realm of medical billing and patient demographic data – particularly involving data with errors and omissions needing correction. Concordantly (😏), a large proportion of the relationships between tables were represented with nullable foreign keys.

Safe, Deeply-nested Logic

I often found myself working on code similar to this contrived simplification …

nate-gehringer

const estimateDynamoDBThroughputSettings = ({
  atomicRead = false,
  averageItemSizeBytes,
  desiredExecutionDurationHours,
  itemCount
}) => {
  const totalItemSizeMegabytes = (itemCount * averageItemSizeBytes) / 1024 /* kilobytes */ / 1024 /* megabytes */;
  const readUnitsPerItem = atomicRead
    ? Math.max(Math.ceil(averageItemSizeBytes / 4096) /* 1 RCU = up to 4 KB */, 1) / 2 /* eventually consistent reads use 0.5 RCU */
    : (averageItemSizeBytes / 4096 /* 1 RCU = up to 4 KB */) / 2 /* eventually consistent reads use 0.5 RCU */