What is Egress?

Data sent out of a service, such as images downloaded from your storage. Many services bill for it.

Where Egress goes wrong in real apps

Each of these is a short scenario built from a real failure in an app made with AI. Read the answer here, or walk through it yourself in about four minutes.

  • Bills that explode · 4 minutes · Pro

    2 million requests from one tab

    You left your dashboard open overnight. Your database usage page shows 2 million requests from a single browser.

    Why is my useEffect fetching in an infinite loop?

    The effect changes one of its own dependencies, for example setting a state object it depends on, so every run triggers another run. Remove the self-update, depend only on values that really change, and watch the Network tab for repeating requests. Select only the columns you display to reduce data transfer.

    Read the fix

  • Bills that explode · 5 minutes · Pro

    The 4 MB thumbnail

    Your marketplace shows 24 small product photos per page. On phones it takes ages to load, and your storage bill warns you are over your data transfer limit.

    Why are my uploaded images making my app slow?

    Your app is probably storing and serving the full-size photos users upload, often 4 MB or more, even where they are shown as small thumbnails. Browsers download the whole file before shrinking it. Create smaller copies at upload or with an image service, serve WebP or AVIF, and give each screen the size it needs.

    Read the fix

Related terms

Network tab
A panel in your browser's developer tools that lists every request your page makes and every reply.
Request
A message your browser (or any program) sends to a server asking for something: 'give me invoice 105' or 'save this profile'.
Browser
Chrome, Safari and friends. Everything that runs here is visible to, and changeable by, the person using it.
Database
Where your app keeps its data, organised in tables, like a set of spreadsheets.
Table, row, column
A table is like one spreadsheet (orders). Each row is one item (one order); each column is one detail (price, date).
Cache
A saved copy of a page or data, reused to be fast. Until refreshed, it can show old information.

All 62 terms in the glossary