How a matching engine works
An incoming order is matched against the best price on the other side of the book and, at the same price, against the order that arrived first. That rule is price-time priority. The trade takes the price of the order already resting in the book, and what is left of a limit order rests there in turn.
Each match is a trade to book and settle, and the new prices and depth go out as market data. EU rules call this a continuous auction order book trading system: one that matches sell orders with buy orders at the best available price, continuously and without human intervention. The common order types and roles:
- Limit order: buys or sells at a set price or better, and can rest in the book
- Market order: trades at once against the best prices available
- Stop order: waits for a trigger price, then becomes a market or limit order
- Post-only order: a limit order that does not go through if it would trade at once
- Maker and taker: the resting order adds liquidity, the order that hits it takes liquidity
What MiCA asks of a trading platform
In the EU, bringing together many third parties' buying and selling interests in crypto-assets is operating a trading platform. That needs authorisation as a CASP, in the EUR 150,000 capital class. Article 76 then asks for:
- Non-discretionary rules for fair and orderly trading
- Systems that are resilient, handle peak order volumes and stay orderly under severe market stress
- Rejection of orders that exceed pre-set volume and price thresholds or are clearly erroneous
- Public bid and ask prices and depth during trading hours, and each trade's price, volume and time
- No dealing on own account on the platform the operator runs
- Order data kept for the authority for at least five years
Who needs a matching engine
Only a venue where many customers' orders meet: a crypto exchange, or a securities venue such as a multilateral trading facility under the EU's MiFID II. MiFID II also requires a regulated market to be able to halt or constrain trading temporarily when a price moves significantly in a short period.
A broker app, an on-ramp or an OTC desk has no need of one. Each prices a customer's request and executes with a liquidity provider or on someone else's venue.
Matching engine, order book or RFQ?
- Order book
- The data: the resting orders, level by level. The matching engine is the logic that matches incoming orders against them.
- Request for quote (RFQ)
- A participant asks for a price and gets one or more quotes that only the requester can accept. No order rests in a public queue.
- Automated market maker (AMM)
- Prices come from a liquidity pool and a formula, not from matching orders. The EU's transparency standard for MiCA lists it as a separate type of trading system.
- Smart order router
- Sends orders to other venues' matching engines rather than matching them itself.
Where a matching engine shows up in a platform
Modules that do the work
- Matching engineA low-latency order book for spot markets, with market makers and outside liquidity.
- Market dataLive and historical prices for crypto, stocks and FX, from the data vendors you choose.
- LedgerThe double-entry book of record behind every balance, fee and transfer.
- Custody & walletsWallets on every major chain, with MPC custody from leading providers or your own keys.
- FXCurrency conversion with live rates, your margins and the liquidity provider you choose.
Platforms that need it
Guides that go deeper
- MiCA checklist: launching a crypto exchange in the EUWhat the EU's Markets in Crypto-Assets Regulation asks of an exchange: authorisation, capital, governance, client assets, the trading platform rules, and the laws that sit beside it.
- What does it cost to launch a crypto exchange?Licensing, capital, technology, liquidity and people: where the money goes when you launch an exchange, and which of those costs depends on how you build.
- What a crypto exchange licence costs: fees and capital by regulatorThe application fee, the yearly fee and the capital a crypto exchange needs under MiCA, the FCA, VARA, ADGM and the DFSA, as each regulator publishes them, and when each falls due.
- How to start a crypto OTC desk: RFQ, liquidity and licensingHow a crypto OTC desk works from request for quote to settlement, principal or agency, liquidity and pre-funding, and the licence it needs: MiCA in the EU, VARA in Dubai, the FCA in the UK.
- VARA licence for a crypto exchange in DubaiWhat Dubai's virtual assets regulator asks of a crypto exchange: the two-stage licence, the rulebooks, capital and fees as VARA publishes them, local staff and the Travel Rule.
Where it is written
The laws and standards this page's facts come from.
- Regulation (EU) 2023/1114, MiCA, Articles 3 and 76 and Annex IV (EUR-Lex)
- Commission Delegated Regulation (EU) 2025/417, transparency data of crypto-asset trading platforms (EUR-Lex)
- Directive 2014/65/EU, MiFID II (EUR-Lex)
- Commission Delegated Regulation (EU) 2017/587, Annex I, types of trading system (EUR-Lex)
General information, not legal advice: what applies to you depends on your services and your market.