Constant DEFAULT_MAX_RETRIES 

pub const DEFAULT_MAX_RETRIES: i32 = 20;

Default maximum number of retry attempts before a job is moved to the dead letter queue.

With exponential backoff (2^(error_count+1) seconds), 20 retries means:

• First retry after 2 seconds
• Last retry after ~6 days
• Total retry window of ~12 days