For customers running FIXEdge C++, FIX Integrated Control Center (FIXICC), or custom solutions built with the FIX Antenna SDK, we leverage cloud-native Kubernetes infrastructure to implement a cold-standby high-availability (HA) pattern that balances resilience, operational simplicity, and deterministic FIX behavior.

Supported Products

This deployment pattern applies to:

Architecture Overview

How It Works

  • Kubernetes StatefulSet (replicas = 1) A StatefulSet ensures a stable identity for the FIX engine instance, including a persistent Pod name and network identity. Only one active FIX engine instance runs at any time.
  • Persistent Volumes Backed by CSI FIX session logs, sequence numbers, and application state are stored on a Persistent Volume (PV) provisioned via a cloud provider’s CSI driver (e.g., AWS EBS, Azure Disk). All critical FIX session state is synchronously persisted to disk, relying on the durability guarantees of the underlying storage.

Failover Behavior

In the event of node or Pod failure:

  • The Kubernetes StatefulSet controller automatically schedules a new Pod on a healthy node.
  • The existing Persistent Volume is re-attached to the new Pod.
  • The FIXEdge process restarts and resumes operation using the preserved on-disk session state.
  • Clients reconnect via the configured LoadBalancer or service endpoint.

FIX Session Semantics During Recovery

  • FIX session sequence numbers and message logs are preserved across restarts.
  • Upon client reconnection, standard FIX gap detection and replay mechanisms apply.
  • Messages that were in flight at the time of failure may be replayed after recovery.
  • Idempotency and duplicate handling remain governed by FIX protocol semantics and client-side logic.

This approach ensures end-to-end message integrity, while maintaining deterministic and standards-compliant FIX behavior.

Client Connectivity Considerations

To achieve optimal recovery times, FIX clients should follow standard HA best practices:

  • Enable automatic reconnect and retry logic
  • Use appropriate heartbeat intervals to detect failures promptly
  • Tune DNS TTLs or leverage direct LoadBalancer IPs to minimize reconnection delays

These practices ensure that client reconnection aligns with the engine’s rapid restart behavior.

Trade-offs

Pros

  • Cloud-native resilience
    Leverages Kubernetes’ built-in self-healing, scheduling, and rolling-update capabilities with minimal custom logic.
  • Managed persistence
    CSI-backed volumes benefit from cloud-provider durability, replication, snapshotting, and restore capabilities.
  • Operational simplicity
    Once StatefulSets and PVs are defined, standard Kubernetes workflows (kubectl, Helm, CI/CD pipelines) handle upgrades, configuration drift, and node failures.
  • Unified observability
    Monitoring, logging, and alerting integrate seamlessly with existing Kubernetes ecosystems (Prometheus, Fluentd, OpenTelemetry, etc.).

Cons

  • Cold-standby recovery latency
    Failover time is bounded by PV detach/attach operations and container startup, typically on the order of 30–90 seconds, depending on cloud provider and volume characteristics.
  • Single-replica execution
    With replicas: 1, there is no parallel processing of FIX traffic. Horizontal scaling requires sharding, multiple StatefulSets, or higher-level routing strategies.
  • Storage costs and cloud specificity
    Persistent volumes incur ongoing costs, and CSI behavior can vary subtly across cloud providers.
  • Client reconnection delays
    DNS propagation or load-balancer reconfiguration may introduce additional seconds of delay if TTLs and client settings are not tuned appropriately.

Positioning: When to Use This Pattern

This cold-standby StatefulSet model is well suited for:

    • Regulated trading environments
    • Deterministic FIX session management
    • Firms prioritizing operational simplicity and protocol correctness
    • Post-trade and connectivity hubs where sub-second RTO is not required

It is not intended for:

    • Ultra-low-latency, sub-second RTO requirements
    • True active-active FIX session processing without protocol-level partitioning

Persistence and Crash Consistency Considerations

Because FIX session correctness depends on durable sequencing and ordered writes, persistent storage behavior is a critical part of this architecture.

fsync and Durability Guarantees

    • FIXEdge and related FIX products explicitly flush critical session state (sequence numbers, message journals, recovery checkpoints) to disk using synchronous writes.
    • Durability therefore depends on the cloud provider’s block storage honoring fsync() semantics.
    • Major CSI-backed block storage implementations (e.g., AWS EBS, Azure Disk, GCP Persistent Disk) provide write durability once fsync() returns, ensuring that acknowledged FIX messages survive process or node crashes.

Write Ordering

    • FIX session state is written in a strictly ordered manner:
      • Message persistence occurs before sequence number advancement.
      • Recovery checkpoints are only updated after prior writes are safely committed.
    • CSI block devices preserve write ordering guarantees at the volume level, which is sufficient for FIX journal and sequence integrity.
    • No reliance is placed on filesystem-level write reordering or asynchronous buffering for correctness.

Crash Consistency Expectations

In the event of a crash:

    • The filesystem and volume may roll back to the last successfully flushed state.
    • FIX session recovery replays messages based on persisted journals and sequence numbers.
    • Duplicate messages may be retransmitted after recovery, consistent with FIX protocol semantics.
    • Message loss does not occur for messages that were acknowledged to the counterparty.

This model aligns with standard FIX recovery expectations and does not rely on speculative or application-level transaction coordination across storage layers.

Operational Recommendations

To ensure predictable behavior:

    • Use cloud block storage classes with documented durability and ordering guarantees (e.g., EBS gp3/io2, Azure Premium SSD).
    • Avoid network filesystems (e.g., NFS, SMB) for FIX session persistence unless explicitly validated.
    • Monitor storage latency, as excessive write latency can directly affect session throughput and recovery time.

Our Experience

We have deployed this pattern across multiple cloud providers, consistently achieving recovery time objectives (RTO) under 60 seconds while preserving FIX session continuity and message integrity.

By combining persistent storage with Kubernetes’ self-healing capabilities, this approach minimizes manual intervention and operational complexity while providing a robust, production-ready HA solution for FIX connectivity platforms.

Documentation

FIXEdge C++ Kubernetes Quick Start
FIXEdge Java Kubernetes Quick Start
FIXICC H2 Kubernetes Quick Start