1. A method for stratified-sampling-based query execution comprising: receiving and interpreting a query; wherein interpreting the query comprises identifying a first set of data shards containing data relevant to the query; collecting a first data sample from the first set of data shards using a non-stratified sampling technique; performing statistical analysis on the first data sample; wherein performing statistical analysis comprises calculating a first variance of the first data sample; identifying a stratum classifier of the first data sample from the statistical analysis; generating a stratum classification by calculating strata boundaries for the stratum classifier; wherein calculating strata boundaries comprises calculating a set of strata boundaries such that a stratified sampling variance of the first data sample using those strata boundaries is less than the first variance; collecting a second data sample using a stratified sampling technique; wherein the stratified sampling technique is performed according to the stratum classification; and calculating a result to the query based on analysis of the second data sample; wherein collecting a second data sample comprises identifying a second set of data shards containing data relevant to the query and collecting the second data sample from the second set of data shards; wherein the second set of data shards contains data not contained in the first set of data shards; wherein the second set of shards are sharded by the stratum classifier; wherein identifying the second set of data shards comprises identifying the second set of data shards according to the stratified sampling technique.