Handling Large Blobs medium
You update a file 'image.jpg' in S3, but users still see the old version. Why?
- A The database is slow.
- B S3 is eventually consistent.
- C The user is offline.
- D The CDN (Edge Cache) has a cached copy of 'image.jpg'. You must either wait for the TTL to expire or explicitly 'Invalidate' the cache.
Answer: D. The CDN (Edge Cache) has a cached copy of 'image.jpg'. You must either wait for the TTL to expire or explicitly 'Invalidate' the cache.
Cache invalidation is one of the two hard things in CS. Standard fix: Version files (`image_v2.jpg`) to avoid invalidation delay.
One system design question a day, with spaced repetition so the ones you miss come back.
Get the appRelated questions
- Why do modern sites serve images in WebP or AVIF format?
- What does the acronym BLOB stand for?
- Why do we sometimes convert binary images to Base64 strings?
- What is an 'Origin Shield' or 'Mid-Tier Cache' in a CDN architecture?
- For a feed with 100 images, why use 'Lazy Loading'?
- How does HLS/DASH handle a user moving from WiFi to 4G (Variable Bandwidth)?