llfix
Low latency FIX protocol engine
Docs
Intro
llfix is a low-latency FIX engine available as an MIT-licensed open-source edition and a commercial edition.
Open-source edition (MIT)
- Single-digit microsecond encoding/decoding (incl. serialisation & validations)
- High determinism
- Header-only, no mandatory dependencies (optional: LibNUMA)
- FIX version agnostic, all versions supported
- Immediate mode (no internal message queueing)
- No memory allocations on latency-critical paths & vDSO utilisation
- Fast message serialisation via virtual memory
- TCP administration interface and programmatic administration(Python)
Commercial edition additional features
- Scalable multithreaded FIX server
- Solarflare TCPDirect support for FIX clients (Linux only)
- FIX dictionary validations (QuickFIX format)
- Code generator from your custom dictionary
- Administration GUI
- High availability
- SSL/TLS support
- Full source code with no checkers, access to bug tracker & support
Supported platforms
Language / Standard
C++17
Platforms
x86, Linux (GCC & Clang) and Windows (MSVC)
Commercial edition builds
- You can choose between header-only and static library builds
- Optional dependencies: TinyXML2, OpenSSL, Solarflare TCPDirect
Reference baseline benchmarks
TX/send (Solarflare Onload)
1 million messages, latency includes encoding, message serialisation, and enqueueing to NIC (not wire-to-wire)
8=FIXT.1.1|9=218|35=D|34=2|49=CLIENT1|52=20251231-18:21:36.457245600|56=EXECUTOR|50=SNDR_SUB|57=SRVR_SUB|11=1|55=NOKIA.HE|54=1|38=10|44=10000|40=2|59=0|453=2|448=PARTY1|447=D|452=1|448=PARTY2|447=D|452=3|60=20251231-18:21:36.457245600|10=221|
- P50: 573 ns
- P75: 798 ns
- P90: 1044 ns
- P95: 1588 ns
- P99: 2663 ns
TX/send (Solarflare TCPDirect)
1 million messages, latency includes encoding, message serialisation, and enqueueing to NIC (not wire-to-wire)
8=FIXT.1.1|9=218|35=D|34=2|49=CLIENT1|52=20251231-18:21:36.457245600|56=EXECUTOR|50=SNDR_SUB|57=SRVR_SUB|11=1|55=NOKIA.HE|54=1|38=10|44=10000|40=2|59=0|453=2|448=PARTY1|447=D|452=1|448=PARTY2|447=D|452=3|60=20251231-18:21:36.457245600|10=221|
- P50: 493 ns
- P75: 536 ns
- P90: 685 ns
- P95: 1437 ns
- P99: 2629 ns
Singlethreaded FIXServer throughput
4.7 million messages in total from 32 clients handled by one thread, on loopback device, includes message serialisation and dictionary & other validations & sending execution reports
8=FIXT.1.1|9=188|35=D|34=2|49=CLIENT1|52=20251231-17:42:03.736004873|56=EXECUTOR|11=1|55=BMWG.DE|54=1|38=1|44=5|40=2|59=0|453=2|448=PARTY1|447=D|452=1|448=PARTY2|447=D|452=3|60=20251231-17:42:03.736004873|10=077|
- Throughput: 222423 msg/s
- Latency/message: 4.49 µs
Multithreaded FIXServer throughput
4.7 million messages in total from 32 clients handled by multiple threads, on loopback device, includes message serialisation and dictionary & other validations & sending execution reports
8=FIXT.1.1|9=188|35=D|34=2|49=CLIENT1|52=20251231-17:42:03.736004873|56=EXECUTOR|11=1|55=BMWG.DE|54=1|38=1|44=5|40=2|59=0|453=2|448=PARTY1|447=D|452=1|448=PARTY2|447=D|452=3|60=20251231-17:42:03.736004873|10=077|
- Throughput: 564,177 msg/s
- Latency/message: 1.77 µs
Features
Commercial edition features are fully accessible: no hidden code, no licence checkers.
Multithreaded FIX server
Multithreaded FIX server allows to optimise message throughput by taking advantage of CPU cores.
TCPDirect for FIX clients
Solarflare TCPDirect bypasses the BSD sockets interface and its semantics to achieve lower latency than Onload.
AdminGUI
TCP based Admin GUI allows to manage sessions of your instances. It allows you to promote or demote instances, enable or disable sessions, manage sequence numbers, inspect loaded configs and monitor events.
High availability
Sequence numbers and messages are synchronised reliably with the TCP based HA Syncer. The HA Manager guarantees continuous availability through TCP-based leader election.
Code generator
The llfix code generator produces classes (with encoders/decoders) and enums from your FIX dictionary, reducing integration time.
FIX Dictionary validations
Built-in FIX dictionary validation (QuickFIX format) ensures protocol correctness.
Technical resources
Documentation
Video walkthroughs
Insight articles
How to achieve P90 submicrosecond latency
Tools
tinyfix, Coreware's open-source Python library for FIX tooling
Licence types
Monthly subscription options allow you to avoid long-term commitment to expensive upfront licences.
| Licence type | Monthly subscription | Annual subscription | Notes |
|---|---|---|---|
| Per Server Licence | Available | Available at a lower fee | Production usage |
| Enterprise Licence | — | — | Unlimited servers, priority support, bespoke terms |
Unlimited usage included for Test / QA / UAT environments for all licence types. Commercial licence includes access to the private GitHub repository and issue tracker. Support is provided via emails (enquiries@llfix.net) and private GitHub repository Issues / Discussions. Reseller and white-label licensing options are also available for technology vendors. Support response targets: Critical: 4 hours High: 24 hours Low: 48 hours Response times are targets and not guarantees. Full SLA terms are defined in the licence agreement.
Opportunities
No openings currently. But you can submit your CV below for speculative applications :
About us
Coreware Limited is registered in England and Wales under company number 8542146.
Registered office: 565 Green Lanes, London, N8 0RL, United Kingdom.
Coreware was founded by Akin Ocal, with a background in game engines and electronic trading.
He has previously worked at Thomson Reuters and on exchange connectivity teams at Citi and JPMorgan.
Seun Ewulomi is a co-founder of Coreware, with experience in low-latency infrastructure engineering at JPMorgan, Morgan Stanley, Kraken, and GSR.
For all enquiries regarding licensing, commercial support, partnerships, or general questions, please contact us at:
