Your code, on the same rails our own order pad runs on

The credential your program sends on every later request. It authorises orders on your account, which is why it stays out of logs and URLs, and it expires at the end of the trading day.

Any order generated by logic rather than approved individually by a person. It requires exchange approval through the broker before it runs, however simple the logic is.

The public identifier issued to a registered application. It says which program is calling and does not by itself authorise anything.

The confidential half of the credential pair, used on your server to prove a token exchange came from you. It never belongs in a browser, a mobile app or a repository.

The retained record of what a strategy did, with its identifier on every order, detailed enough for someone who has never seen your code to reconstruct the day.

The volume-weighted price at which an order has filled so far. It differs from the price you asked for whenever the order filled in pieces.

Waiting progressively longer between reconnection or retry attempts, so that a failing dependency is not hammered while it recovers.

Running a strategy over historical data. It has no spread to cross, no queue to wait in and no rejections, so it flatters almost every strategy it touches.

Several orders assembled and sent as one instruction, so that a multi-leg position is established together rather than leg by leg.

Anything that grants access simply by being presented, with no further proof of identity. An access token is one, which is why it is treated like a password.

The open, high, low and close of an instrument over a fixed interval, with the volume traded in it. The unit of historical data.

A hash of the API key, the request token and the secret, sent with the token exchange to prove the request came from the holder of the secret.

The identifier of the trading account itself. It is the same whether an order came from the app or from your program.

A package that wraps the same HTTPS and socket calls in the idioms of a language. A convenience over the interface, not a different interface.

The bids and offers resting at successive price levels rather than only the best one. Delivered in the fuller streaming modes.

A single addressable operation in the HTTPS interface, identified by a path and a method.

A periodic message that proves a connection is still alive. Its absence is the earliest signal that a feed has gone stale.

Past prices supplied on request rather than streamed, for research and charting, usually under a subscription of its own and with licence conditions attached.

Shares held in demat from delivery purchases settled on earlier days. A different thing from positions, and a different read.

Safe to do more than once with the same result. A postback handler has to be, because deliveries can repeat.

The daily list of tradable instruments with tokens, symbols, lot sizes, tick sizes and expiries. Fetch it once a day and cache it locally.

The numeric identifier the quote and streaming interfaces use for an instrument, rather than its human-readable symbol.

A means of stopping a strategy and squaring off that does not depend on the strategy's own process being healthy enough to obey it.

The price of the most recent trade in an instrument. The lightest streaming mode delivers this and little else.

The time between something happening and your program acting on it, including the network, your own code and the exchange.

The terms under which exchange prices reach you. Use inside your own application is permitted; passing them to anyone else is not, without separate permission.

How much detail the socket sends for a given instrument, from the price alone to the full order book. It is set per instrument.

Every order placed in the current session with its present state. The authoritative answer to what your program has actually done today.

The reference returned when an order is accepted, used for every later modification, cancellation or read of that order.

The number of orders placed against the number that actually traded. Limits exist to discourage loading the book with instructions never meant to trade.

An order that has traded for some of its quantity and remains open for the rest. One order can produce many trades.

Asking the same question repeatedly on a timer. Almost always the wrong tool where a subscription exists, and the usual cause of a rate-limit problem.

Today's exposure and what is carried forward, with quantity, average price and running profit or loss. The number a risk check should be written against.

An HTTPS request we send to a URL you registered whenever one of your orders changes state, so your server is told rather than having to ask.

Whether a position is intraday, taken for delivery or carried in a margin product. It decides the margin and whether it is squared off automatically.

The number of requests per second an interface will accept, published separately for each kind of call.

Comparing what your program believes it did against the order book, the trade book and the contract note. The gaps that appear are the defects worth fixing.

The address we return the browser to after a successful login, carrying the one-time request token.

An order refused at validation, by us or by the exchange, with a reason attached. It is information, not something to retry blindly.

The one-time value delivered to your redirect URL after login, exchanged on your server for an access token.

The request and response style used for orders and account state: your program asks, we answer, and nothing is remembered between calls.

Many failed requests retried at once, turning a brief outage into a rate-limit breach. Backoff and a little randomness prevent it.

The day-long authorisation created by the token exchange and ended when the access token expires.

The difference between the price a strategy assumed and the price it actually received. The largest single gap between a backtest and a live run.

Closing an open position by trading the opposite side of it.

A fixed network address from which approved algorithmic order flow originates, required where the rules call for it, so that the flow is attributable.

The unique tag attached to an approved algorithm and carried on every order that algorithm sends.

Telling the socket which instruments to push to you. One connection carries many, which is why it replaces every polling loop.

A short label of your own attached to an order and returned on every later read of it, used to tell one strategy's orders from another's.

A ceiling you impose on your own request rate, set below the published limit so that one retry does not breach it.

One update from the feed for one instrument. The same word also means the smallest permitted price increment, and context decides which is meant.

A common way to throttle: requests spend tokens that refill at a fixed rate, so bursts are smoothed out rather than rejected.

The executions of the day, each with its own fill price, quantity and time, as distinct from the instructions that produced them.

The second proof of identity required at login, and the reason a person has to be present each morning before a program can trade.

How long an order lives if it does not fill: for the day, or until it is cancelled within the session, depending on what the exchange supports.

The general name for a server-to-server callback. A postback is one.

A single long-lived connection over which the server pushes messages without being asked. The right tool for anything live.