How to Choose a Market Data Feed Before You Build on a Key
A chart is only as honest as the feed. Check venue coverage, delay, and redistribution — then pick an API you can replace.
Published: Aug 24, 2026 · Updated Aug 24, 2026
Author: Traderfolio
Editorial standards. Guides are written from published catalog data and vendor documentation — not paid placement copy. Sponsored listings are labeled separately. See listing guidelines.
Market-data marketing is a list of asset-class logos. The product is a contract for timestamps and redistribution. If you cannot say which venue, which delay, and whether you may store bars, you do not have a feed — you have a trial key.
Start at the market-data hub and the API collection. Polygon.io is a common starting name for equities and options history. That is a coverage check, not a stack decision.
1. Write the universe before you write the language
You need:
- Venues (which tape, which FX book, which crypto pair)
- History depth
- Real-time vs delayed
- Whether you store bars or only display them
- Whether a second app may reuse the same key
A 15-year daily backtest and a 50ms options sweep are different SKUs that happen to share a dashboard.
2. Delay and entitlements are the price
“Real-time” often means “real-time after you pay the exchange.” Confirm:
- Which entitlements are included
- What is delayed 15 minutes
- Corporate-action and split handling
- Options: OPRA vs vendor-derived greeks
If the catalog row does not list it, believe the vendor’s current entitlements page — and expect it to change.
3. Redistribution will bite you later
Bots, public sites, and “I will just cache this” are how keys get killed.
Read the license for:
- Display vs non-display
- Storage
- Derived data
- Passing quotes to a third party
If you are building anything public, assume you need a different SKU.
4. Replaceability is a feature
Pick a feed you can swap. Normalize symbols in your own layer. If the vendor’s SDK is the architecture, you do not have an architecture.
The backtesting guide is the next failure mode: lookahead and untradeable prints from a pretty CSV.
5. Compare two APIs on the same week of tape
Pull the same session from two names in the collection. Diff timestamps and prints. The cheaper key that misses the open is not cheaper.
FAQ
Can I start on a free key?
Yes, as a rehearsal. Do not size a live system on a delayed or sampled plan.
Is Polygon the default?
It is a catalog name with broad equity/options coverage. Your venue list is the test. See Polygon.io.
Where is the aisle?
Market data. Featured is editorial, not an exchange license.