# The future of serialization & deserialization APIs

**URL:** <https://forums.swift.org/t/the-future-of-serialization-deserialization-apis/78585>\
**Category:** Discussion\
**Tags:** foundation, codable, macros\
**Created:** [March 17, 2025, 8:25pm UTC](https://forums.swift.org/t/the-future-of-serialization-deserialization-apis/78585 "2025-03-17T20:25:29Z")\
**Posts on this page:** 1\
**Showing post:** 173

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**Author:** ![couchdeveloper](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/couchdeveloper/32/23601_2.png) [@couchdeveloper](https://forums.swift.org/u/couchdeveloper)\
**Post date:** [January 18, 2026, 2:35pm UTC](https://forums.swift.org/t/the-future-of-serialization-deserialization-apis/78585/173 "2026-01-18T14:35:03Z")

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I made a post in "Using Swift" which is related to this thread:

> [@I reimplemented Foundation's JSONEncoder and made it 33% faster using compile-time strategy dispatch](https://forums.swift.org/t/i-reimplemented-foundations-jsonencoder-and-made-it-33-faster-using-compile-time-strategy-dispatch/84195):
>
> I recently explored whether Swift's type system and compiler could eliminate runtime overhead in encoding, and the results were surprising: a 33% performance improvement over Foundation's JSONEncoder using clean, maintainable code. The Core Idea Instead of runtime configuration with mutable properties, the encoder's type IS its configuration. The encoder itself is a generic type with with no stored state, and has a single pure function: (Input) -\> throws Output How it works The pattern leve…

Correction: the encoder is 40% faster ;)

In short, the Encoder type is the configuration. Due to this, the compiler obtains more optimisation opportunities. The implementation uses conforming types to `Encodable` as usual, its strategies are reusable and composable, it's clean and maintainable code - and has no hacks, no unsafe code.

This pattern can be applied to decoders as well.

## Quick Insights

### Core Architecture

- **StaticJSONEncoder** with compile-time configuration via generic parameters
- **Protocol-based strategies** using associated types (no runtime dispatch)
- **Reusable state and sink** design for zero-allocation hot loops
- **JSONDataSink** optimized for UTF-8 and minimal copies

### Performance Achievements \*)

Foundation: 359ms, 5469M instructions, 2000K allocations  
StaticEncoder: 212ms, 3165M instructions, 1200K allocations  
With reuse \*\*) : 192ms, 2816M instructions, 800K allocations

→ 41% faster (47% with reuse)  
→ 42% fewer instructions  
→ 40% fewer allocations

\*) 100\_000 encoding passes for a simple composite (nested) struct

\*\*) Sink, which can be cleared, and Encoder State - which will always be cleared.  
The state is still a class - unfortunately, it can't be avoided that easily.

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