# API Complexity

## Overview

API queries for metrics, such as this NVT example, can potentially yield extensive results (ranging from hundreds of thousands to millions of data points). They may also generate queries that scan the entire database, thereby consuming substantial resources. This could potentially expose the system to DoS attacks.

To prevent such scenarios, every GraphQL request is analyzed before execution. The complexity of each query is calculated, and if it exceeds a certain threshold, the API server rejects it and returns an error without executing the query. Generally, the complexity is proportional to the number of data points and the size of the time interval included in the result.

The complexity calculation considers the following factors:

• Number of data points returned - N. For instance, fetching 30 days of data at daily intervals results in 30 data points.
• Number of fields in a data point - F. Most metrics include two fields: datetime and value.
• Metric weight - W. Most metrics are stored in specialized fast data storage, so they have a smaller weight (0.3). The remaining metrics have a weight of 1.
• Years time range span - Y. If the request uses a large interval (like 30 days), the number of data points is small. However, the time range spans several years. The query still needs to read and aggregate a lot of data in the database.
• Subscription plan tier - S. The higher the user's plan, the larger the complexity limit (3 for Basic, 5 for Pro, 7 for Premium). As the complexity threshold is constant, the computed complexity is divided by S. This means that the same query executed by a Pro user will have a complexity five times smaller than the same query executed by a Free user.

Given the above-defined values, the complexity is calculated using the following formula:

In this formula, Q represents the query being analyzed, and N(Q)...S(Q) are the described values computed for that query.

## Example

Let's examine how to calculate the complexity when a SanAPI PRO subscription user executes the following query:

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{
getMetric(metric: "price_usd"){
timeseriesData(
slug: "bitcoin"
from: "utc_now-3650d"
to: "utc_now"
interval: "1h"){
datetime
value
}
}
}
• N(Q) = 3750 * 24 = 90000 - The time range spans 3650 days and the interval is set to 1 hour.
• F(Q) = 2 - Each data point contains two fields: datetime and value.
• W(Q) = 0.3
• Y(Q) = 4 - Computed as: max(2022-2012, 2) / 2
• S(Q) = 5 - The SanAPI PRO plan offers complexity limits that are 5 times higher than those of the SanAPI Free plan.

The complexity of the query, Q, is calculated as follows:

The complexity threshold is 50000, so this query is valid and the API server will execute it. If a SanAPI Free user attempts to execute this query, S(Q) will equal 1 and the complexity will exceed 210000. This will trigger the following error:

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Operation is too complex:
complexity is 210241 and maximum is 50000