Good morning! It’s Wednesday — Architecture day. Today’s vocabulary is about caching and content delivery: the words you need when a design doc argument turns into “is this data even fresh?” These terms show up in almost every performance discussion, from a single Redis lookup to a globally distributed CDN.
🌟 Word of the Day: Invalidate
IPA Pronunciation: /ɪnˈvæl.ɪ.deɪt/
Vietnamese meaning: Làm mất hiệu lực / Vô hiệu hóa (dữ liệu cache)
To invalidate a cache entry means to mark it as no longer trustworthy — the underlying data has changed, so the cached copy must not be served again until it’s refreshed. Getting invalidation right is famously one of the hardest problems in computing, right up there with naming things.
“We forgot to invalidate the product-price cache after the discount campaign ended, so customers kept seeing the old price for another six hours.”
🗣️ 3 Example Sentences
- “Every time a user updates their profile, we invalidate the corresponding cache key so the next read hits the database.”
- “There are only two hard problems in computer science: cache invalidation and off-by-one errors.”
- “The bug wasn’t in the cache logic itself — we just never invalidated the entry when the underlying record was deleted.”
🔗 Practice Links
- Cambridge Dictionary: https://dictionary.cambridge.org/dictionary/english/invalidate
- YouGlish (hear native speakers): https://youglish.com/pronounce/invalidate/english
📋 Caching & CDN Vocabulary Table
| Phrase | Vietnamese | Example |
|---|---|---|
| Cache hit | Truy cập cache thành công | ”80% of our requests are cache hits, so the database barely feels the traffic.” |
| Cache miss | Truy cập cache thất bại | ”A cold cache means every request is a cache miss until things warm up.” |
| TTL (time-to-live) | Thời gian sống (của dữ liệu cache) | “We set a five-minute TTL so stale data can’t linger for more than five minutes.” |
| Eviction policy | Chính sách loại bỏ dữ liệu cache | ”Our eviction policy is LRU — the least recently used entries get removed first when the cache is full.” |
| Edge node | Nút biên (máy chủ CDN gần người dùng) | “The image is served from the nearest edge node, so users in Hanoi don’t wait on a server in Virginia.” |
🔊 Pronunciation Guide
Invalidate has four syllables — don’t rush it:
- in — /ɪn/ — short “i,” like in “sit”
- VAL — /væl/ — stress falls here, like the name “Val”
- i — /ɪ/ — short and quick
- date — /deɪt/ — like the fruit or the calendar word “date”
Put together: in-VAL-i-date, with the clear primary stress on the second syllable.
📢 Practice Sentence (read aloud 3x)
“We invalidate the cache entry the moment TTL expires, so an edge node never serves a stale cache hit.”
Read it slowly the first time, focus on the “in-VAL-i-date” stress the second time, then read it at natural speaking speed the third time.
✏️ Exercises
Exercise 1: Fill in the Blank
- When the underlying data changes, the system must __________ the old cache entry.
- If the requested data is already cached, that’s called a __________; if not, it’s a __________.
- We set a five-minute __________ so stale results expire automatically.
- Our __________ removes the least recently used entries first when the cache fills up.
- Users get faster load times because content is served from a nearby __________ instead of a distant origin server.
👉 Click to see answers
- invalidate
- cache hit / cache miss
- TTL (time-to-live)
- eviction policy
- edge node
Exercise 2: Translate to English
- “Chúng tôi quên vô hiệu hóa cache sau khi cập nhật giá sản phẩm.”
- “Tỷ lệ cache hit của chúng tôi là 90% trong giờ cao điểm.”
- “TTL của dữ liệu này là mười phút.”
👉 Click to see answers
- “We forgot to invalidate the cache after updating the product price.”
- “Our cache hit rate is 90% during peak hours.”
- “The TTL for this data is ten minutes.”
💬 Idiom of the Day: Under the Hood
Vietnamese meaning: Bên trong / Cơ chế hoạt động ẩn giấu bên dưới
Borrowed from cars — you don’t need to see the engine to drive, but engineers need to know what’s under the hood. In tech, it describes the internal mechanics of a system that aren’t visible from the outside.
🗣️ 2 Examples
- “The API looks simple from the outside, but under the hood it’s coordinating three separate caching layers.”
- “Let’s not worry about what’s happening under the hood right now — just confirm the cache invalidation actually fixed the bug.”
📺 Recommended Watching
- ByteByteGo — visual explainers on caching strategies, CDNs, and eviction policies: https://www.youtube.com/@ByteByteGo
- Hussein Nasser — deep dives into how real systems implement caching and invalidation at scale: https://www.youtube.com/@hnasr
- Cloudflare — “How CDNs Work”: search “how does a CDN work Cloudflare” on YouTube for a clear walkthrough of edge nodes and cache behavior
🎯 Daily Challenge
Today, explain one caching decision from a project you’ve worked on, out loud, using at least two of today’s words. For example: “We set a short TTL and an LRU eviction policy so a cache hit almost never serves stale data.” Saying it out loud is what makes the vocabulary stick.
Thuận Lương is a Technical Lead with 15+ years of experience in .NET, cloud architecture, and AI systems, and a daily English learner himself. Follow along for daily practice built for real tech conversations.