Executive Summary

Global financial markets are rapidly moving toward near-continuous trading models. Traditional exchanges and Alternative Trading Systems (ATS) are seeking regulatory approval to extend trading hours to 24 hours a day, five days a week (24×5) and, in some cases, full 24×7 operation beginning in 2026.

This shift is driven by:

  • growing demand from Asian market participants to trade U.S.-listed instruments during local hours
  • increasing expectations from retail investors accustomed to continuous access in FX and crypto markets

As trading hours expand, FIX connectivity must evolve to support uninterrupted, long-running sessions without introducing operational risk.

Market Landscape: Exchanges Modernizing for 24×7 Trading

Summary of Venue Initiatives (as of 2025)

Exchange / Venue 24×7 Status Notes
CME Group (Crypto) Full 24×7 (planned 2026) Continuous crypto futures & options; maintenance windows only
Coinbase Derivatives Exchange (CDE) Yes 24×7 trading for selected products (opt-in)
Cboe (U.S.) Partial Extended hours; not full 24×7
Nasdaq / ATS venues Extended Exploring near-24 access
Crypto exchanges (Binance, Coinbase, Kraken) Full 24×7 Not traditional regulated venues, but strong market influence
24X National Exchange Targeting 23×5 SEC-approved national exchange launched in late 2025
Blue Ocean ATS (BOATS) 8:00 p.m.–4:00 a.m. ET Overnight ATS operating Sunday
IBKR EOS ATS (IBEOS) — Interactive Brokers’ internal ATS, ~10,000 stocks & ETFs
MOON ATS — OTC Markets Group overnight ATS for select OTC securities
Bruce ATS — Recently approved overnight ATS (launch details evolving)

Broker Platforms Offering 24×5 Access

Several brokerages already provide near-continuous trading for selected U.S. equities:

  • Robinhood – “24 Hour Market” (selected stocks & ETFs)
  • Charles Schwab – 24×5 trading for S&P 500, Nasdaq-100, and hundreds of ETFs
  • Interactive Brokers – Overnight trading from Sunday 8:00 p.m. ET to Friday 3:50 a.m. ET

Implications for FIX Connectivity

As exchanges extend trading hours, FIX session semantics are changing:

  • Sessions must remain active across multiple calendar days
  • Operational boundaries (start/end times, daily resets) are no longer guaranteed
  • Recovery must be automated and non-disruptive

While the FIX protocol conceptually supports long-running sessions, many FIX engines—open-source and commercial—require enhancements to operate safely in this model.

Exchanges adopt different approaches to keep FIX sessions uninterrupted for market data, order entry, and drop copy feeds over extended periods. Some venues, drawing on practices from crypto and next-generation exchanges, may operate with weekly FIX engine restarts that emulate continuous trading environments. Others may continue using daily sequence number resets without interrupting active FIX sessions.

Client FIX architectures must therefore provide the flexibility to support multiple session semantics and include robust operational controls to accommodate exchange-specific requirements.

Key Challenges for 24×7 FIX Connectivity

Key Technical Challenges for Long-Running FIX Sessions
Sequence Number Limits

Most FIX engines store MsgSeqNum using 32-bit integers, limiting sessions to 2,147,483,647 messages.

  • This limit may be insufficient for high-volume, multi-day sessions
  • If exchanges disallow sequence resets, 64-bit sequence number support becomes necessary
Message Store Growth
  • FIX logs can exceed available disk capacity in long-running sessions
  • Engines must support:
    • segmented storage
    • multiple storage devices
    • rolling / chunked log management
Performance Degradation
  • Some FIX engines degrade as message stores grow
  • Log indexing and access patterns must scale linearly
Resend & Retransmission Risk
  • Large resend requests can:
    • overwhelm system resources
    • interfere with live order flow
  • Engines must support efficient, throttled, and prioritized retransmission
Session Timing Constraints

Many FIX engines require:

  • StartTime
  • EndTime

 

For 24×7 operation, engines must support:

  • dynamic start time at engine launch
  • no fixed end time (infinite session duration)
Required Capabilities for 24×7 FIX Operation
A FIX engine supporting continuous trading must provide:
  • Durable persistence of all inbound/outbound FIX messages
  • Message store survival across:
    • process restarts
    • server reboots
    • failovers
  • High-availability (HA) readiness
  • Warm restart with:
    • persisted session state
    • intact message store
  • Graceful recovery without:
    • forced sequence resets
    • order duplication
  • Automatic reconnect and resynchronization
  • Manual tools for controlled sequence resets
  • End-of-trading-day logic for rolling/archiving data without session interruption
  • Ability to restart FIX infrastructure without disconnecting trading logic. Reconnection logic incorporating exponential backoff
Flexibility for Exchange-Specific Rules
Client FIX engines must support:
  • Sequence resets only by explicit agreement or maintenance window
  • Forced logouts initiated by exchanges
  • Unscheduled restarts
  • Logout with reset vs. logout without reset
  • Silent disconnect handling
  • Mid-session sequence resets
  • Persistent session state across multiple days
  • Calendar logic aligned with exchange-defined trading day cutovers
Integration with OMS, Risk, and Back-Office Platforms
The shift to real-time trading:

As the entire ecosystem moves toward continuous trading, many end-of-day batch integrations must be redesigned to operate in real time. New regulatory frameworks for intraday margining also require reengineering and must be incorporated into pre-trade risk checks.

FIX engines therefore need to be enhanced to interact with OMS, risk, and back-office platforms in real time, leveraging a variety of available middleware technologies.
Monitoring, Alerting & Operational Tooling
Long-running sessions require advanced observability:

Dashboards

  • Session status with detailed event history
  • Latency and performance metrics with time-window drill-down

Alerts

  • Excessive resend volume
  • Repeated reconnect attempts
  • Abnormal session behavior
Operational Considerations
Market infrastructure is still adapting to accommodate non-stop trading, raising concerns about staffing and risk management.

Continuous trading introduces new challenges:

  • No “quiet overnight” window
  • Reduced availability of human intervention
  • Increased reliance on automation and self-healing systems
  • Ability to inject or modify business rules without service interruption

Conclusion

Firms that:

  • rely on daily FIX resets
  • assume calendar-day boundaries
  • depend on manual FIX operations

will face increased operational risk as markets transition to near-continuous trading.

While many open-source and commercial FIX engines require enhancements to meet these demands, B2BITS / EPAM FIX engines were designed for long-running, always-on sessions and are battle-tested across FX, futures, and crypto markets.

Organizations seeking:

  • always-on FIX gateways
  • centralized session management
  • strong operational runbooks

can rely on our technology and expertise.

If you are planning to connect to a 24×7 or 24×5 marketplace and need a robust FIX solution, please contact sales@btobits.com.

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