Once started as a side business, AWS is becoming Amazon’s primary business unit.

Half of Amazon’s operating profits are from AWS. Share of AWS in total sales of Amazon are also more than 10%.

In financial results delivered Thursday, AWS drove $7.43 billion sales for the quarter ending Dec. 31, up 45% from $5.11 billion year-over-year. 

That’s the same year-over-year growth rate (Q4 2018 over Q4 2017) for AWS that it saw in the year-ago quarter (Q4 2017 over Q4 2016).

Operating income for AWS was $2.17 billion, up from $1.35 billion in the year-ago quarter.

For calendar 2018, AWS sales were $25.65 billion, up 47% from $17.45 billion year-over-year. Sales growth accelerated in 2018 over 2017 compared with 2017 over 2016, which saw 43% sales growth.

For AWS’s sales growth to accelerate in that fashion is noteworthy because AWS is by far the leader in cloud market share, ahead of second-ranked Microsoft Azure by a wide margin; accelerating growth speaks to overall strength for AWS and the cloud market in general.

Operating income for AWS was $7.29 billion in 2018, up from $4.31 billion in 2017.

AWS represents a growing share of Amazon’s overall revenue — by a smidge — 11% in 2018 compared with 10% in the previous year, and 10% in the fourth quarter of 2018, compared with 8% in the year-ago quarter.

And AWS is the lion’s share of Amazon’s operating income: Nearly 58% in the fourth quarter of 2018, and nearly 59% for the full year.

For Amazon overall, including its mainstay retail business, for the quarter, sales were up 20% to $72.4 billion after a strong holiday season. Net income increased to $3 billion in the fourth quarter, or $6.04 per diluted share, compared with $1.9 billion or $3.75 per diluted share in the year-ago quarter.

For the full year, net sales were up 31% to $232.9 billion. Net income increased to $10.1 billion, or $20.14 per diluted share, compared with $3 billion or $6.15 per diluted share in 2017.

The Echo Dot was the best-selling item across all products on Amazon.