REST vs WebSocket for financial news: which should you use?
When to poll a REST news API and when to stream over WebSocket: latency, cost, complexity and reliability trade-offs for market news apps.
Short answer: use REST to search, backfill and build pages on demand. Use WebSocket when your app has to react to new articles within seconds. Most production apps use both: REST for history and gap-filling, WebSocket for the live edge.
How REST news delivery works
With REST, your code asks a question ("latest Apple news since 13:00") and gets a page of results. It's stateless, cache-friendly, easy to debug with cURL, and runs anywhere, including serverless functions and cron jobs. To get new articles, you poll: repeat the request on an interval.
How WebSocket news delivery works
With WebSocket, your code opens one long-lived connection and subscribes to channels (ticker:AAPL, type:press_release). The server pushes each matching article as soon as it's available. There are no wasted requests and no polling delay, but you now own a stateful connection: heartbeats, reconnects and gap-filling.
Side-by-side
| REST (polling) | WebSocket (push) | |
|---|---|---|
| Latency | Poll interval ÷ 2 on average | Seconds after ingestion |
| Wasted calls | Most polls return nothing new | None |
| History & search | Yes: filters, full-text, pagination | No, live only |
| Infrastructure | Anything that can make HTTP requests | An always-on process |
| Failure handling | Retry the request | Reconnect + backfill via REST |
| Best for | Pages, reports, research, cron jobs | Alerts, trading signals, live UIs |
The latency math of polling
If you poll every 30 seconds, a headline waits 15 seconds on average and up to 30 seconds before your code sees it. Polling every 2 seconds cuts that, but that's 43,200 requests a day per filter set. On quota-based APIs that adds up fast. On MarketNewsAPI paid plans there's no request quota, but a stream is still simpler and faster.
Try it for 7 days. Signup starts Pro. A card is required. Real-time REST, WebSocket, and MCP, with no request cap. After that it's $15/month, or Free if you stop.
The hybrid pattern most teams use
- On startup, call
GET /v1/newswith your filters to load recent history. - Open the WebSocket and subscribe to the same filters.
- Track the latest
published_atyou've processed. - On disconnect, reconnect, then call REST with
from=that timestamp to fill the gap. De-duplicate byid.
# Gap-fill after a reconnect
curl "https://api.marketnewsapi.com/v1/news?tickers=AAPL,MSFT&from=2026-10-06T13:02:11Z&sort=published_asc&limit=100" \
-H "Authorization: Bearer $MARKETNEWSAPI_KEY"Which plan do you need?
Pro is $15 a month for unlimited real-time REST and the WebSocket, with 3 concurrent connections and unlimited messages. The 7-day trial includes both.