An LCU measures the dimensions on which the Application Load Balancer processes your traffic (averaged over an hour). The three dimensions measured are:
- Number of new connections: Measures newly established connections per second.
- Number of active connections: Measures number of active connections per minute.
- Bandwidth: Measures the amount of traffic processed by the load balancer in Mbps.
You are charged only on the dimension with the highest usage. An LCU contains:
- Up to 25 new connections per second.
- Up to 3,000 active connections per minute.
- Up to 2.22 Mbps
Let’s assume your application receives 1 new connection per second, each lasting 2 minutes and consuming 300 KB in bandwidth. We calculate your monthly Application Load Balancer costs using pricing in the US-East-1 Region as follows:
- New connections (per second): each LCU provides up to 25 new connections per second (averaged over the hour). Since your application receives 1 new connection per second, this translates to 0.04 LCUs (1 connection per second / 25 connections per second);
- Active connections (per minute): each LCU provides up to 3,000 active connections per minute. Your application receives 1 new connection per second, each lasting 2 minutes. This translates to 120 active connections per minute, or 0.04 LCUs (120 active connections / 3,000 active connections);
- Bandwidth (Mbps): each LCU provides 2.22 Mbps averaged over the hour. Since your application transfers 300 KB in bandwidth per connection, that is 2.4 Mbps or 1.08 LCUs (2.4 Mbps / 2.22 Mbps).
Using these values, the hourly bill is calculated by taking the maximum LCUs consumed across the three dimensions. In this example, the bandwidth dimension (1.08 LCUs) is greater than both the new connections (0.04 LCUs) and active connections (0.04 LCUs), resulting in a total charge of $0.008 per hour (1.08 LCUs * $0.008 per LCU) or $6.19 per month ($0.0086 * 24 hours * 30 days).
Adding the hourly charge of $0.0225, the total Application Load Balancer costs are:
- $0.03 per hour ($0.0225 hourly charge + $0.0086 LCU charge); or
- $22.39 per month ($0.0311 * 24 hours * 30 days).