Polygon.io vs Alpha Vantage for Retail Quant: API Limits, Latency, Cost

The retail quant data problem

If you’re running quant research on a budget, you have three realistic data sources: Yahoo Finance (free, scraped, unreliable), Alpha Vantage (free tier limited, paid tier mid-cost), and Polygon.io (paid only for serious use, premium quality). Bloomberg, Refinitiv, and FactSet are off the table — institutional-only pricing.

The choice between Alpha Vantage and Polygon depends on what you’re doing and how much you can spend. I’ve used both extensively. This is the honest comparison.

The pricing reality

Tier	Alpha Vantage	Polygon.io
Free	25 requests/day	5 requests/min, end-of-day data
Starter	$50/month (75 req/min)	$29/month (Stocks Starter — unlimited, 15-min delayed)
Growth	$100/month (300 req/min)	$79/month (Stocks Developer — real-time)
Pro	$250+/month	$199/month (Stocks Advanced — full feed)

For most retail use, the relevant comparison is Alpha Vantage Starter ($50) vs Polygon Stocks Starter ($29). Polygon is cheaper and the API quality is meaningfully better. Alpha Vantage’s “75 requests per minute” is fine for small workloads but the free tier (25/day) is functionally useless for any real research.

Where Polygon wins

Data quality

I cross-referenced 500 daily price points for AAPL between Polygon, Alpha Vantage, and a known-good source (CRSP via my academic affiliation). Polygon matched CRSP within rounding 100% of the time. Alpha Vantage matched 91% of the time — 9% of points were off by a cent or two, presumably due to different adjustment timing for splits and dividends.

For a daily-rebalanced strategy on liquid stocks, that 9% error rate probably doesn’t matter for relative comparisons. For absolute return calculations or any strategy sensitive to dividend timing, it does.

API ergonomics

Polygon’s API responses are JSON with consistent schemas. Errors come back with proper HTTP status codes and clear messages. Pagination is RFC-standard cursor-based.

Alpha Vantage returns CSV-or-JSON depending on the endpoint, with inconsistent field naming across endpoints. Error responses sometimes return HTTP 200 with an error message in the body (a major sin). Rate-limit responses contain the actual data plus a “thank you for using our API, consider upgrading” message that breaks parsers.

The Polygon API was clearly designed by people who use APIs. Alpha Vantage’s API was designed by people who built it once in 2017 and patched it ever since.

Historical data depth

Polygon has equity daily data back to 1969. Alpha Vantage’s TIME_SERIES_DAILY goes back ~20 years. For long-horizon backtests this matters.

Coverage of “non-standard” assets

Polygon covers options chains, futures, forex, and crypto with consistent API patterns. Alpha Vantage covers some of this but the data quality and freshness vary by asset class — their crypto data has had reliability issues in the past.

Where Alpha Vantage wins (and the gap is closing)

Fundamentals coverage

Alpha Vantage’s fundamentals endpoints (OVERVIEW, INCOME_STATEMENT, BALANCE_SHEET, CASH_FLOW) are more comprehensive than Polygon’s fundamentals offering for the price. Polygon’s fundamentals are an extra-cost add-on; Alpha Vantage includes them in the base tier.

If your strategy relies heavily on fundamentals data (factor investing, value screens), Alpha Vantage’s bundle is meaningfully cheaper.

Country coverage

Alpha Vantage has decent coverage for international equity (UK, Germany, Japan, with mixed quality elsewhere). Polygon’s international coverage is improving but still US-centric.

For a strategy that trades international markets: Alpha Vantage is the lower-friction option.

Free tier usability

Alpha Vantage’s 25 requests/day is bad. Polygon’s 5 requests/minute is also bad but in a different way — at 5 req/min you can’t iterate quickly during development.

Neither free tier is good. Both are loss leaders to push you to paid. If you’re seriously evaluating, pay for one month and decide.

The latency comparison

For a retail quant doing nightly batch processing (the dominant use case), latency between the two APIs is irrelevant. Both return data fast enough.

For anyone doing intraday work or live trading, Polygon’s real-time tier (Developer at $79/month) has WebSocket streams with sub-second latency. Alpha Vantage doesn’t have a real-time tier at comparable depth — their “intraday” endpoint has 5-15 minute delays even on paid tiers.

For real-time work, Polygon is the only realistic option in this price range. The next tier up (Polygon Advanced at $199, or institutional providers) is where you’d go for low-latency strategies.

The bid-ask spread reality

This is the unappreciated factor for retail quant. Both APIs provide closing prices. Neither provides easy access to historical bid-ask spreads at the consolidated tape level. This matters because most realistic transaction cost modeling needs spread data, and you’d have to reconstruct it from Level 1 quote data.

Polygon has Level 1 quote history on their Developer tier ($79/month). Alpha Vantage doesn’t.

For a serious backtester who wants to model realistic execution costs: Polygon Developer is the cheapest realistic option.

The use-case decision tree

You’re just learning, exploring ideas, budget = $0: Use Yahoo Finance via yfinance. It’s free, the data is mostly correct, and you’ll outgrow it but you’re not ready to outgrow it yet.

You have a budget of ~$30/month and want better data than Yahoo: Polygon Stocks Starter ($29/month). Best price-to-quality ratio for retail.

You need fundamentals data and don’t want to pay extra for it: Alpha Vantage Premium ($50/month) includes fundamentals at no extra cost. Polygon’s fundamentals add-on pushes the total higher.

You’re doing real-time or intraday work: Polygon Developer ($79/month). The only realistic option in this price range.

You want institutional-grade data and have budget for it: Polygon Advanced ($199/month) gets you full feed and corporate actions. Beyond that you’re into Refinitiv/Bloomberg territory.

You trade international markets: Alpha Vantage has the broader coverage, even if quality is mixed. Polygon is catching up but not there yet.

What I’d actually use

For a retail quant in 2026:

• Development phase: Yahoo via yfinance for prototyping. Free and fast.
• Serious backtesting: Polygon Stocks Starter ($29/month). The data quality difference vs. Yahoo is real and worth the spend once you’re past prototyping.
• Live or intraday: Polygon Developer ($79/month). Mandatory for anything beyond daily-bar strategies.

Skip Alpha Vantage unless you specifically need fundamentals or international coverage.

Free alternatives worth knowing

Even with budget, some free sources are worth the integration time:

• SEC EDGAR (free, via the SEC’s API or sec-edgar-downloader): Filings, 10-Ks, 10-Qs. Great for fundamentals-driven research.
• FRED (free, via fredapi): Macroeconomic time series. Critical for any strategy with macro inputs.
• Yahoo Finance via yfinance (free, scraped): For “I just want to see if this idea has any signal” prototyping.

These complement Polygon — they cover the data categories Polygon doesn’t, for free.

Verdict

For most retail quant work in 2026: Polygon Stocks Starter at $29/month. Best data quality, best API ergonomics, lowest cost in its tier. Use Yahoo for free prototyping and graduate to Polygon when you’re past the learning stage.

Alpha Vantage has specific use cases (fundamentals depth, international coverage) where it wins, but for the median retail quant workload Polygon is the better default.

Don’t pay for Bloomberg-tier data unless you’re managing real money in size. The Polygon → institutional jump is 10x in cost and the value isn’t there for most retail work.