Market Infrastructure
Exchanges, clearing houses, custodians and the firms that publish a rating, an index or a price. None of them takes the other side, and everything passes through them.
The system around it: Sets the rules, runs the plumbing, keeps the score. the whole map
The seats
three of them, each answering the same six questions so that they can be read against each other.
Next to it
The other group on the same side of the price.
What an interview asks here
These seats are nobody's counterparty and everybody's dependency, and the questions are checking whether you know what that changes.
Try each one out loud before you open it. What is underneath is the shape of a complete answer, not a script — somebody who can produce those parts in their own words can also answer the four variations that follow, and somebody who has memorised a paragraph can answer one.
Q1What does a clearing house actually do to a trade?
What it is checking. Novation, and whether you know it moves risk rather than removing it.
A complete answer contains:
- It steps between the two sides: it becomes the buyer to every seller and the seller to every buyer.
- Neither side then relies on the other; both rely on the clearing house.
- It holds no market risk as a result, and a great deal of counterparty risk, which it manages with margin and a default fund.
- So the risk did not disappear — it was concentrated somewhere designed to hold it, which is a different thing.
Read it properly: Clearing and settlement · Exchanges and clearing
Q2Initial margin and variation margin answer different questions. Which?
What it is checking. Two things called margin that behave nothing alike.
A complete answer contains:
- Variation margin settles what has already been lost or gained today: it moves cash daily and keeps the exposure near zero.
- Initial margin covers what could still be lost while closing out a defaulted position, over the days that would take.
- So variation margin is backward-looking and certain; initial margin is forward-looking and modelled.
- Which is why raising initial margin in a stress is procyclical — it takes cash out of the market exactly when cash is scarcest.
Read it properly: Margin and collateral · 2022
Q3What is the default waterfall and why is the order the point?
What it is checking. Who bears a loss, in writing, decided before anybody defaults.
A complete answer contains:
- First the defaulting member's own margin, then its contribution to the default fund.
- Then a defined slice of the clearing house's own capital, then the surviving members' contributions.
- Writing the order down in advance is what makes members willing to face one institution instead of each other.
- It also means members are exposed to each other's failures, which is a real cost of clearing and is usually left unsaid.
Read it properly: Exchanges and clearing · If the other side fails
Q4A custodian holds your securities. What are you actually relying on?
What it is checking. Segregation, which is the entire product and almost never visible on a statement.
A complete answer contains:
- That the assets are recorded in your name and separated from the custodian's own, so they are not available to its creditors.
- That the chain below it holds — a global custodian holds through sub-custodians, and the local link is where the legal protection lives.
- That elections and entitlements are passed on and acted on, because a missed deadline is a decision made for you.
- Almost nothing on a custody statement tells a reader which of those they actually have.
Read it properly: Custody and securities services · If a broker fails
Q5Why does an index provider move real money?
What it is checking. The influence comes from being referenced, not from being right.
A complete answer contains:
- An index is a rulebook, and hundreds of mandates and funds are contractually pointed at it.
- So when the rules add or remove a name, every tracker must trade — on the same day, in the same direction.
- That is a predictable flow, which means it is front-run, which means the fund pays for the very rule it is following.
- The same property makes methodology changes a consultation rather than an announcement.
Read it properly: What an index really is · Index and ETF management
Q6What is a credit rating, and what is it not?
What it is checking. An opinion that regulation points at, which is a strange object.
A complete answer contains:
- It is an opinion about the likelihood of being paid, expressed as an ordering rather than a probability.
- It says little about how much is recovered if it is not paid, and nothing about price.
- Its power comes from being referenced in mandates and capital rules, which turns a downgrade into forced selling.
- And the issuer usually pays for it, which is a structural conflict that process mitigates rather than removes.
Read it properly: What a rating tells you · 2008
Q7An exchange cancels a set of trades. What has it done besides reversing them?
What it is checking. Whether you see the second-order cost of an intervention.
A complete answer contains:
- It has protected whoever was on the losing side of those prints and imposed the loss on whoever was on the other.
- It has told the market that a price on this venue is provisional, which changes how everybody quotes afterwards.
- And it has created a precedent that gets argued about at the next extreme move.
- Which is why venues write the conditions for cancellation in advance rather than deciding in the moment.
Read it properly: 2022 · Market microstructure
Do these against a clock — one at a time, ninety seconds each, answer before you look.
Whose questions these are. Every question on this page was written for this publication. None is taken from anybody else’s question bank, and none is a claim about what any named firm asks — that is neither verifiable from here nor ours to assert. They are our own reading of which mechanism a question of this kind is testing. Information and education only.
Test yourself: five questions
Five quick questions on this part of the industry — checked entirely on your device, nothing stored or sent. Wrong answers come with explanations, and the seat pages above hold every answer. For education only.