Velocity Trading - Tani Diament

Overview

Market makers are the middlemen in modern trading activity who provide liquidity to an exchange by quoting buy and sell prices on assets. The market maker profits off the bid-ask spread while managing the underlying risk of its positions. The system must handle massive volumes of orders while maintaining consistent state throughout the cluster.

Services

Exchange — Matches the incoming external order against the active quote for the symbol, generates the fill, and decrements remaining quote quantity.
Exposure — Global gatekeeper for limiting firm-wide bid/ask exposure. Before publishing a quote the market maker must reserve exposure with this service.
Market Maker — Generates quotes based on current market positions.
Trading State — Authoritative store of positions and fills. Notifies Market Maker of position and fill updates.

Architecture

K3s cluster There are 3 control plane nodes running Apache Zookeeper. The remaining nodes run market-maker pods led by a leader. The Exchange, Trading State, and Exposure service each run as 1 leader + 2 hot-backup replicas.
Durable in-memory state — Hazelcast in memory maps (IMap) store data for fast retrieval while persisting on PostgreSQL. Every IMap (positions, fills, quotes, reservations, external-orders) is write-through via a JPA MapStore to a single PostgreSQL StatefulSet, with InitialLoadMode = EAGER so a full cluster restart rebuilds state with no operator intervention.