Systems · English usage comparison
Cache vs Buffer: English Usage Guide for IT Professionals
Both are temporary storage, but for different purposes. A cache stores copies of data to speed up future reads — it's optional, and the data also exists elsewhere. A buffer temporarily holds data in transit between two systems running at different speeds — it's a queue, not a copy.
Side-by-side comparison
| Aspect | Cache | Buffer |
|---|---|---|
| Purpose | Speed up repeated reads | Smooth mismatched speeds between producer/consumer |
| Data origin | Copy — original exists elsewhere | In-transit — may not exist elsewhere yet |
| Miss behaviour | Fetch from source (cache miss) | Block or drop (buffer full) |
| Example | Redis caching DB results | Network socket receive buffer |
Example sentences
Cache
- "We cache the product list in Redis for 5 minutes — the database isn't hit on every page load."
- "The cache hit rate is 94% — only 6% of requests go to the database."
Buffer
- "The TCP receive buffer fills up when the consumer processes packets slower than they arrive."
- "We increased the write buffer size to prevent blocking when disk I/O is slow."
Exercises: choose the correct English usage
Select the best answer for each question, then check your reasoning.
1. "We store database results in Redis to avoid repeated queries." Redis is acting as a ___.
Explanation: Storing copies of results to speed up repeated reads is caching.
2. "The network ___ is full — the application is dropping packets." Which word fits?
Explanation: Network receive/send buffers hold in-transit data. When full, packets are dropped.
3. What happens on a "cache miss"?
Explanation: On a cache miss, the system fetches data from the original source (e.g. database) and may populate the cache.
4. Which sentence uses "cache" correctly?
Explanation: Caching API responses to serve repeat requests instantly is the correct usage.
5. How is "cache" pronounced?
Explanation: "Cache" is pronounced /kæʃ/ — rhymes with "cash". A common mispronunciation is "catch".
Frequently asked questions
What is a "cache hit" vs "cache miss"?
A cache hit means the requested data was found in the cache. A cache miss means it wasn't — the system must fetch it from the original source, which is slower.
What is "cache invalidation"?
Removing or expiring stale data from the cache. Often called "one of the two hard problems in computer science" (along with naming things and off-by-one errors).
What is a "TTL" in caching?
Time To Live — how long a cached item is valid before it expires and must be refreshed from the source.
What is "write-through" vs "write-back" caching?
Write-through writes to cache and source simultaneously. Write-back writes to cache first and syncs to the source later (faster writes, risk of data loss if cache fails).
What is a "ring buffer"?
A fixed-size buffer that wraps around — when full, new data overwrites the oldest. Common for log rings and streaming data.
What is "buffering" in video streaming?
Pre-loading upcoming video data into memory so playback is smooth even if network speed fluctuates. A buffer, not a cache — it's data in transit, not a reusable copy.
What is the CPU cache?
A small, very fast memory layer (L1, L2, L3) between the CPU and main RAM. Stores frequently accessed instructions and data for faster access.
What is a "warm cache"?
A cache that has been populated with data — requests are being served from cache. A "cold cache" is empty, so all requests initially go to the source.
What is "cache eviction"?
Removing items from the cache to make room for new ones. Policies include LRU (Least Recently Used), LFU (Least Frequently Used), and FIFO.
Can you buffer without caching?
Yes. A network packet buffer holds data in transit — it's not a cached copy of anything. And a cache doesn't buffer: it stores durable copies, not in-flight data.