1A load with 3 1,5V@2950mAh AA Alcaline batteries
It is a much better design to connect the lock directly to the batteries, this way the lock operation will not inject current spikes or other disturbances downstream of the LDO where the MCU is connected.
When the batteries are new they will maintain the appropriate voltage level (3-5V there is ample margin). At some point when they become depleted the lock will not operate anymore and the MCU may reset if the voltage goes too low during the lock operation.
On this site, you can compare the voltage vs current of AA batteries
https://lygte-info.dk/review/batteries2012/CommonAAcomparator.php
set the current to 1A instead of the default 2A
They list some Varta models but not your specific model, but Varta should be able to supply the curves
When the battery is new enough, the voltage per cell drops with 1A drawn but is above what you need as there is a need of at least 1.15V per cell to keep the LDO working (3 x 1.15 = 3.45).
At some point during the discharge, the 1A curve crosses down the 1.15V level, the batteries will have to be replaced to maintain proper operation of the LDO + MCU.