Market data + /v2/clock returning 500/504 for one account since this morning, trading endpoints fine (day after Algo Trader Plus upgrade)

Alpaca Account Troubleshooting
1

Environment

Language
Python 3.9.6 (also reproduced with plain curl from the shell, so the language is not a factor).

Alpaca SDK Version
No SDK. Direct HTTPS requests to the REST API with httpx 0.27 (and curl 8 for the reproduction below), authenticated with the APCA-API-KEY-ID / APCA-API-SECRET-KEY headers.

Other Environment Details
macOS 26 (Darwin 25.6.0), local machine on a residential connection, no cloud provider, no proxy or VPN. Market data plan: Algo Trader Plus, upgraded on 2026-09-10 (the day before the problem started).

Problem

Summary
Since about 16:11 UTC on 2026-09-11, every market-data request and the clock/calendar endpoints fail for my account after ~3.3 seconds, while trading and account endpoints work normally. It is still happening as I post this.

Failing, always after ~3.3 s:

  • GET paper-api.alpaca.markets/v2/clock → 500 {"message":"Internal Server Error"}
  • GET paper-api.alpaca.markets/v2/calendar → 500 {"message":"Internal Server Error"}
  • GET data.alpaca.markets/v2/stocks/SPY/snapshot?feed=sip → 504 {"message":"backend request timeout"}
  • GET data.alpaca.markets/v1beta1/options/snapshots/SPY?feed=opra → 504 {"message":"backend request timeout"}
  • Same 504 on /v2/stocks/SPY/bars (feed=sip and feed=iex), /v2/stocks/SPY/trades/latest and /v1beta1/news

Working with the same keys in the same minute, ~0.35 s:

  • /v2/account, /v2/orders, /v2/positions, /v2/assets/SPY, /v2/options/contracts → 200

Already ruled out:

  • Keys: I regenerated the API key pair and the new keys fail identically. Deliberately invalid keys return 401 in 0.3 s, so authentication is healthy.
  • Network: identical results over IPv4 and IPv6, and every failing response carries an Alpaca X-Request-ID header, so the requests are reaching your servers.
  • Rate limits: no 429 responses; under 100 requests per minute.
  • The status page shows all systems operational, so this looks specific to my account.

Every endpoint that consults the account’s market-data plan fails; every endpoint that only touches the trading ledger works. That, plus the timing right after the plan upgrade, makes me suspect the account’s data subscription state. I have request IDs, timestamps and my account number ready to share with staff by DM, and I have opened a support ticket as well.

Paper or Live Tradng?
Paper trading. The live host behaves the same way for these keys (api.alpaca.markets/v2/clock also returns 500 instead of the expected 403 for paper keys).

Example Code

# Replace the two headers with your own keys. Both hosts, same key pair, same minute.

# Fails: HTTP 500 after ~3.3 s
curl -s -w " -> %{http_code} %{time_total}s\n" \
  -H "APCA-API-KEY-ID: $KEY" -H "APCA-API-SECRET-KEY: $SECRET" \
  https://paper-api.alpaca.markets/v2/clock

# Fails: HTTP 504 "backend request timeout" after ~3.3 s
curl -s -w " -> %{http_code} %{time_total}s\n" \
  -H "APCA-API-KEY-ID: $KEY" -H "APCA-API-SECRET-KEY: $SECRET" \
  "https://data.alpaca.markets/v2/stocks/SPY/snapshot?feed=sip"

# Works: HTTP 200 in ~0.35 s
curl -s -o /dev/null -w "%{http_code} %{time_total}s\n" \
  -H "APCA-API-KEY-ID: $KEY" -H "APCA-API-SECRET-KEY: $SECRET" \
  https://paper-api.alpaca.markets/v2/account

# Control: invalid keys return 401 immediately, so auth is not the problem
curl -s -o /dev/null -w "%{http_code} %{time_total}s\n" \
  -H "APCA-API-KEY-ID: WRONG" -H "APCA-API-SECRET-KEY: WRONG" \
  https://paper-api.alpaca.markets/v2/clock
2

Here is the incident report for this issue. It’s been resolved but the engineering team is continuing to monitor.