What are the two types of API limits?

The concept of API limits is critical in Salesforce to ensure a smooth experience for all users and maintain overall system integrity. Among the options provided, the combination of concurrent limits and total limits accurately reflects the way Salesforce establishes boundaries on API usage.

Concurrent limits refer to the number of API calls that can be made simultaneously. This is essential for maintaining system performance under heavy loads. If too many concurrent requests are made at once, it could overload the system and degrade service for all users. Therefore, Salesforce sets these limits to ensure that one user's excessive usage does not negatively impact the entire organization.

Total limits, on the other hand, relate to the overall number of API calls that can be made within a specific time frame, typically measured per 24 hours. This helps to manage the overall consumption of API resources, ensuring fair distribution among all users in an organization.

Together, these two types of limits help Salesforce maintain stability and performance, hence defining the usage policy for API calls effectively.