Glossary

Core entities

Instrument / Symbol / Security / Asset / Ticker

Financial instrument such as stock, future, option, CFD, or other asset

Symbol description

Human-readable instrument name

Snapshot and subscription

Subscription

Request to receive market data for specific symbols or event types

Snapshot (state)

Representation of data at a specific point in time

Snapshot (file)

File containing persisted application state, typically used for recovery

Snapshot request

Request for current known state of data at a point in time rather than full event-by-event stream

Empty snapshot

Snapshot response that contains no data for requested symbol, event type, or subscription scope

Data distribution

Quote Distribution (QD)

Protocol and data model used for real-time market data distribution

Quote Distribution System (QDS)

High-performance Java library implementing QD for real-time market data distribution

QD Transport Protocol (QTP)

Wire transport protocol used for QD data exchange. It handles schema negotiation, heartbeats, and bidirectional data and subscription message flow

Financial Information eXchange (FIX)

Standard protocol for financial data exchange

WebSocket (WS)

Bidirectional communication protocol for real-time data streaming

Server-Sent Events (SSE)

Unidirectional streaming protocol from server to client

Data delivery contracts

Contract (QD)

Data delivery mode in QD that defines how market data is stored and delivered to consumers. It includes Ticker, Stream, and History contracts

Learn more

Ticker (data contract)

QD contract that delivers latest value per symbol. Intermediate updates may be replaced by newer ones (auto-conflation).

Use cases: trading screens, dashboards, real-time quotes

Stream (data contract)

QD contract that delivers every event sequentially without conflation

Use cases: trade logging, audit trails, tape recording

History (data contract)

QD contract for time-indexed data that typically starts with snapshot and continues with incremental updates

Use cases: charts, time-series, order book reconstruction

Conflation

Technique that reduces data volume by keeping the latest value and discarding intermediate updates. It happens automatically in ticker and may also be applied in other delivery flows depending on configuration

Connectivity and distribution

dxLink

dxFeed client-facing connectivity and streaming technology used to deliver market data to external consumers

Learn more

Multiplexor (mux, mx)

Market data distribution component that aggregates upstream feeds and redistributes them to downstream clients or systems

Backbone / Upstream

Upstream market data sources or the upstream layer of on-prem multiplexors and distribution topology

Streaming connection

Persistent client connection used to receive real-time or incremental updates continuously

Session

Logical authenticated client interaction with API or streaming service, often associated with connection state and permissions

Reconnect

Process of re-establishing client connection after disconnect, timeout, or network failure

Connection drop

Unexpected interruption of active client connection

Security and access

Authentication

Process of verifying identity of client, user, or application

Authorization

Process of determining what authenticated client, user, or application is allowed to access

Entitlements

Set of permissions that determines which exchanges, products, symbols, event types, or environments client, user, or application is allowed to access.

It is related but distinct from authentication and authorization

Access token

Credential used by client to authenticate API requests for limited period of time. Learn more about Token-Based Authorization

Synonym: API token

Latency

Latency

Delay between an event and its delivery

Data latency

Time delay between market event occurring upstream and same event being delivered to consumer

End-to-end latency

Total delay from source to client

Upstream latency

Delay between event occurring at exchange or provider and that event reaching dxFeed infrastructure

Downstream latency

Delay between data entering dxFeed infrastructure and same data being delivered to client or downstream system

Time to First Data (TTFD)

Elapsed time between connection establishment, authentication, or subscription and first useful market data event received by client

Data gap

Missing period in market data series where expected updates, trades, quotes, or candles are absent

Quote

Market data update representing current top-of-book state for instrument, including bid and ask prices

Bid / Ask

Highest buy price and lowest sell price currently available for instrument

TimeAndSale

Stream of individual trade events with timestamps, prices, and sizes

Real-time (RT)

Market data delivered without delay

Delayed data

Market data delivered with a time delay, typically 15 minutes or more depending on exchange terms

Historical data

Market data from past time periods, typically used for backtesting, charting, and research

Tick

Single market data update representing trade, quote, or order book change

Tick data

Time-ordered sequence of individual market data events such as trades or quotes, without candle or bar aggregation.

Also TickData is a dxFeed service for historical extractions. See How to Request Tick Data

Intraday data

Market data aggregated or recorded within trading day at intervals smaller than one day

Daily data

Market data aggregated into day-based intervals, typically one bar or record per trading day

End of Day (EOD)

Market data aggregated for a full trading day.

For example, an automatic daily data extraction

Event types

Quote event

dxFeed event type representing quote data

Learn more

TimeAndSale event

dxFeed event type representing time and sale data

Learn more

Trade event

dxFeed event type representing trade data

Learn more

Greeks event

dxFeed event type representing option Greeks data

Learn more

Order book

Order book (OB) / Enhanced Order Book (EOB) / Full Order Book (FOB)

Full list of buy and sell orders in market

Depth of Market (DOM)

View of market liquidity showing orders at multiple price levels

Price Level (PL)

Specific price point in order book

Price Level Book (PLB)

Aggregated order book grouped by price levels

Market state

National Best Bid and Offer (NBBO)

Best available bid and ask prices across market

Cross

Market condition where bid price exceeds ask price

Stale Data

Market data that is no longer updating as expected and may not reflect current market state

Tape (QD Tape)

Recorded stream of market data that can be replayed

Regular Trading Hours (RTH)

Standard exchange hours

Extended Trading Hours (ETH)

Pre-market and after-hours trading period

Global Trading Hours (GTH)

Extended global trading period

Trading Hours Only (THO)

Data limited to trading hours only.

For example, candles limited to trading hours

Contract for Difference (CFD)

Derivative instrument that allows trading price movements without owning the underlying asset

Continuous futures

Synthetic instrument combining consecutive futures contracts into a single continuous series

Warrant

Derivative security giving holder right to buy or sell underlying instrument under defined conditions

Exchange-Traded Fund (ETF)

Fund traded on an exchange similarly to stock

Options-related terms

Index Option

Option whose underlying is market index rather than individual stock or future

0 DTE

0 days to expiration

ITM / OTM / ATM (option)

In-the-money, out-of-the-money, and at-the-money

HIRO (Index)

Hedging Impact Real-Time index measuring aggregate hedging pressure from options market makers on underlying asset

Markets and asset classes

Forex (FX)

Foreign exchange market

Crypto (CX)

Cryptocurrency market

Option analytics

Greeks

Option risk measures describing sensitivity to price, volatility, time, and other parameters

Delta

Option Greek measuring sensitivity of option value to changes in underlying price

Gamma

Option Greek measuring how delta changes as underlying price changes

Theta

Option Greek measuring sensitivity of option value to passage of time

Vega

Option Greek measuring sensitivity of option value to changes in implied volatility

Rho

Option Greek measuring sensitivity of option value to changes in interest rates

Corporate actions

Corporate Actions (CA)

Events that affect securities, such as dividends, splits, or spin-offs

CD

Regular cash dividend corporate action subtype

SC

Special cash dividend corporate action subtype

SS

Stock split corporate action subtype

SD

Stock dividend corporate action subtype

SP

Spin-off corporate action subtype

Volatility metrics

IV

Implied volatility

HV

Historical volatility

SV

Statistical volatility

IVR

Implied volatility rank

Pricing models

Bjerksund-Stensland (BJS) Model

Option pricing model used for American-style options

Black-Scholes (BS) Model

Widely used option pricing model primarily for European-style options

Fundamentals

Earnings Per Share (EPS)

Company profit divided by number of outstanding shares

Beta

Metric estimating how strongly security price tends to move relative to a benchmark or broader market

Dividend

Distribution paid by company or fund to holders of security

Ex-dividend date

Date on which buyer is no longer entitled to receive next announced dividend

Ex-Dividend Amount

Dividend amount associated with ex-dividend event for security

Upcoming Dividend

Dividend information announced in advance for future ex-dividend or payment cycle

Identifiers

Financial Instrument Global Identifier (FIGI)

Globally unique identifier for financial instruments. See OpenFIGI

CUSIP

US security identifier

ISIN

International security identifier

Classification system for financial instruments (CFI)

Classification system for financial instruments

Reuters Instrument Code (RIC)

Identifier used by Refinitiv

Exchange Price Information Code (EPIC)

Instrument identifier used by some data providers.

Example: IG

OPOL

Official Original Place of Listing

Instrument Profile Format (IPF)

Format used to describe instrument metadata. Learn more

Storage and replay

Compressed Data Format (CDF)

Compressed file format used for storing market data

Tape

QD data file that can be saved and replayed by qds-tools. See QDS Tool

Backfill

Process of restoring, reloading, or correcting missing or inaccurate historical data

Filters and query parameters

QD filter

Part of QD connection string that filters inbound or outgoing messages

IPF filter

Part of QD filter that refers to specific IPF stored locally or available at URL

fromTime

Request parameter or boundary timestamp indicating start time for historical data retrieval

Timestamp

Time value associated with market data event or historical record

Chart data

Historical or streaming data intended for chart visualization, typically in candle form

Candle

Aggregated chart data record representing open, high, low, close, and usually volume for a defined interval. Learn more section

Bar

Aggregated market data interval used in charting

OHLC

Open, High, Low, Close — four core price values of a candle or bar

Amazon Web Services (AWS)

Cloud computing platform providing infrastructure and services

Google Cloud Platform (GCP)

Cloud infrastructure platform by Google

Oracle Cloud Infrastructure (OCI)

Cloud infrastructure platform by Oracle

AWS core services

Elastic Compute Cloud (EC2)

Cloud computing platform providing infrastructure and services in AWS

Simple Storage Service (S3)

Object storage in AWS

Identity and Access Management (IAM)

Service controlling permissions and access to AWS resources

Virtual Private Cloud (VPC)

Isolated AWS network environment

Load balancers

Elastic Load Balancer (ELB)

Distributes incoming traffic across multiple targets

Application Load Balancer (ALB)

Routes HTTP and HTTPS traffic based on rules

Network Load Balancer (NLB)

For low-latency TCP and UDP traffic

Infrastructure terms

Auto Scaling Group (ASG)

Cloud mechanism for automatically scaling resources

CloudFront (CF)

Content delivery network

Virtual Machine (VM)

Software-based machine that runs applications and operating systems

Relational Database Service (RDS)

Manages cloud database service

Virtual Private Network (VPN)

Secure network used to access internal infrastructure

DC naming

Shorthand for data center locations or colocation facilities used in technical and operational discussions, such as NY4, CHI1, CHI2

Service models

Software as a Service (SaaS)

Software delivery model

Infrastructure as a Service (IaaS)

Infrastructure delivery model

Artificial Intelligence (AI)

Field focused on building systems that perform tasks typically associated with human intelligence

Machine Learning (ML)

Subset of AI focused on models and algorithms that learn patterns from data

Large Language Model (LLM)

Machine learning model trained on large volumes of text, typically used for text generation, summarization, search assistance, and similar tasks