Definition
Smart Order Routing (SOR) is an automated process that evaluates multiple liquidity venues in real-time to determine the optimal execution destination for each order. Instead of routing all orders to a single LP, a SOR engine compares available prices, depth, latency, fill probability, and cost across connected venues before selecting where to execute.
SOR is a core component of best execution in institutional markets and is increasingly adopted in retail FX. It sits at the bridge level in the execution stack, making per-order routing decisions that can significantly impact fill quality. The effectiveness of a SOR engine depends on the number and quality of connected LPs, the optimization algorithm, and the speed of decision-making.
What It Is / What It Is Not
What SOR IS
- Automated venue selection for each individual order
- Evaluates multiple LP quotes in real-time before routing
- Considers price, speed, fill rate, depth, and cost factors
- A technology layer within the A-Book / NDD execution model
- Can operate on composite feeds or direct LP connections
- Key enabler of best execution obligations in regulated environments
What SOR IS NOT
- Not an execution model by itself -- it requires connected LPs
- Not a guarantee of best execution (depends on algorithm and venue quality)
- Not the same as simple round-robin or random LP selection
- Not always transparent -- the scoring logic may be proprietary
- Not exclusive to equities; it is used across FX, futures, and crypto
- Not a regulatory requirement in all jurisdictions, though MiFID II encourages it
SOR Decision Factors
A SOR engine typically scores each connected venue across multiple dimensions before routing:
| Factor | Description | Impact |
|---|---|---|
| Price | Best available bid/ask across venues | Primary factor in most SOR algorithms |
| Depth | Available volume at the quoted price | Critical for larger order sizes |
| Latency | Round-trip time to venue and back | Affects stale quote risk and fill speed |
| Fill rate | Historical acceptance rate from the venue/LP | Low fill rate = orders bounce back, adding latency |
| Last look | Whether the LP applies a hold window before confirming | Adds latency and uncertainty to execution |
| Cost | Commission + spread + potential slippage | Total cost analysis, not just quoted spread |
Where It Appears in the Execution Stack
Advanced SOR implementations include fallback logic: if the primary venue rejects, the engine automatically reroutes to the next-best venue without returning to the client. This reduces perceived latency and improves fill rates.
Benefits & Trade-offs
| Factor | Detail | |
|---|---|---|
| Price improvement | Multi-venue comparison increases probability of better fills | |
| Fill rate | Automatic rerouting on rejection improves overall fill rates | |
| Best execution | Systematic approach to venue selection supports regulatory best execution obligations | |
| Complexity | SOR configuration requires significant expertise and ongoing tuning | |
| Latency overhead | Multi-venue comparison adds microseconds of processing time per order | |
| LP gaming | Sophisticated LPs may adjust quotes knowing SOR patterns (quote stuffing, fading) |
Common Marketing Claims vs Reality
| Claim | Reality |
|---|---|
| "Best execution guaranteed" | SOR improves execution probability but cannot guarantee it. Depends on LP pool quality and algorithm calibration. |
| "Connected to 50+ LPs" | Number of LPs matters less than quality. Many connections may be redundant (same parent bank, different desks) or provide stale quotes. |
| "Lowest spreads in the market" | Tight quoted spreads mean nothing if fill rates are low or slippage is high. Total execution cost is what matters. |
| "Institutional-grade SOR" | Verify by asking: how many venues are evaluated? What scoring factors are used? Are SOR metrics published? |
What to look for in an Execution Policy
- Does the execution policy describe the SOR algorithm or its scoring factors?
- Are the connected LP categories and venue types disclosed?
- Does the broker publish SOR performance metrics (venue utilization, reroute rate)?
- Is fallback/rerouting logic documented in case of LP rejection?
- Does the policy explain how SOR weights are calibrated and updated?
- Are execution venue details reported per-trade to the client?
See a Public Routing Disclosure Example
NDD.broker publishes detailed order routing and execution policy documentation, including LP composition, priority logic, and conflict mitigation. This serves as a reference implementation of the concepts described above.
Educational content only. This is not financial advice. Always consult qualified professionals before making trading decisions.