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Clojure's rich data types are awesome. And its [reader](https://clojure.org/reference/reader) allows you to take your data just about anywhere. But the reader can be painfully slow when you've got a lot of data to crunch (like when you're serializing to a database).
It is used at scale by [Carmine](https://www.taoensso.com/carmine), [Faraday](https://www.taoensso.com/faraday), [PigPen](https://github.com/Netflix/PigPen), [Onyx](https://github.com/onyx-platform/onyx), [XTDB](https://github.com/xtdb/xtdb), [Datalevin](https://github.com/juji-io/datalevin), and others.
Nippy is widely used to store **long-lived** data and promises (as always) that **data serialized today should be readable by all future versions of Nippy**.
But please note that the **converse is not generally true**:
- Nippy `vX`**should** be able to read all data from Nippy `vY<=X` (backwards compatibility)
- Nippy `vX`**may/not** be able to read all data from Nippy `vY>X` (forwards compatibility)
### Rolling updates and rollback
From time to time, Nippy may introduce:
- Support for serializing **new types**
- Optimizations to the serialization of **pre-existing types**
To help ease **rolling updates** and to better support **rollback**, Nippy (since version v3.4) will always introduce such changes over **two version releases**:
- Release 1: to add **read support** for the new types
- Release 2: to add **write support** for the new types
Starting from v3.4, Nippy's release notes will **always clearly indicate** if a particular update sequence is recommended.
### Stability of byte output
It has **never been an objective** of Nippy to offer **predictable byte output**, and I'd generally **recommend against** depending on specific byte output.
However, I know that a small minority of users *do* have specialized needs in this area.
So starting with Nippy v3.4, Nippy's release notes will **always clearly indicate** if any changes to byte output are expected.
Since its earliest versions, Nippy has consistently been the **fastest serialization library for Clojure** that I'm aware of. Latest [benchmark](../../blob/master/test/taoensso/nippy_benchmarks.clj) results:
