My teams have never had any difficulty in schema changes. To be honest, we don't even think of it as an issue. 1) No deleting or alternating columns needed by

My teams have never had any difficulty in schema changes. To be honest, we don't even think of it as an issue. 1) No deleting or alternating columns needed by any production code. Need something different? Create a new column. After weeks of this column not being needed, we use 2) to delete it - but it isn't a priority. 2) Adding/Modifying columns just use pt-schema-change. I have seen this tool transform billion row tables - it also supports slave master.