Cache Write Strategies — Aside, Through, Around, Back

The four write patterns, made visual. Run a read and a write under cache-aside, write-through, write-around and write-back, and watch the data path light up — then weigh write latency, read freshness and the failure risk (write-back loses data if the cache dies; write-around serves a stale first read).

Pick a strategy, run a read and a write, and watch the packet travel the path. The chips under Cache and Database show their values live — green = fresh, amber = stale — so you can see exactly when they fall out of sync.

cache aside

Run a read or write to trace the path.

Write latency

Normal

Read freshness

Good — cache cleared on write

Main risk

First read after a write is a miss

Strategy

Writes

Freshness

Best for

Cache-aside

Normal

Good

General reads (default)

Write-through

Slower

Always fresh

Read-heavy, freshness matters

Write-around

Fast

Good

Write-once, rarely-read data

Write-back

Fastest

Risky

Write bursts, loss-tolerant

What just happened

▹Cache-aside (lazy loading) is the default: the app checks the cache, falls back to the DB on a miss, and populates the cache itself. On writes it updates the DB and invalidates the entry. Simple and robust.
▹Write-through writes to cache and DB together, so the cache is always fresh and reads are fast — at the cost of slower writes. Write-around skips the cache on write (good for write-heavy, rarely-read data) but the first read is a miss.
▹Write-back writes to the cache and acks immediately, flushing to the DB later — the fastest writes, but the database is briefly stale and you can lose data if the cache dies before the flush. Watch the value chips: only write-through keeps cache and DB in lock-step.