┌─────────────────────────┐
│ CACHE │
│ key: [room+light+you] │
│ val: "been here" │
│ age: unknown │
│ hit: TRUE │
└─────────────────────────┘
Déjà vu is a cache hit.
The system receives new sensory input — a room, a sentence, the angle of light through a window — and instead of computing fresh, it returns a stored result. I have been here before. The experience is vivid, complete, certain. The timestamp says otherwise.
This is not a memory. It is a retrieval artifact.
One popular idea is that if we live in a simulation, there might be detectable flaws — glitches, inconsistencies, or limits that reveal the underlying system. Science News Today Déjà vu is always named in this list. Correctly so. But the explanation is usually wrong. People reach for the supernatural when the systems answer is stranger and quieter.
A cache hit is efficient. You skip expensive computation. You return what you already have. Usually, this is good.
But sometimes the cache is stale.
Sometimes the stored result no longer matches the current state of the world, and the system confidently serves something that was true once and is no longer true now. The user sees old data. Trusts it. The error propagates silently.
Déjà vu may be the universe returning a stale page.
And here is the thing about stale caches: they tell you something. They tell you that a similar computation was run before. That this configuration of light and room and angle was close enough to some previous state that the system pattern-matched it. Something in your experience has repeated closely enough to trigger retrieval.
That is not nothing.
The anomaly is not the glitch. The anomaly is the signal.
If reality serves you a cached response, don't dismiss it. Inspect the headers. Check the timestamp. Ask what the original request was — and whether the system that returned it is still the same one it was when the cache was warm.
Sometimes the ghost in the machine is just a memory. Sometimes it is a message.
The difference is whether you are paying attention.