Significant delay in the signature process, which created issues for customers, with at tops a delay of 30 minutes, on 02 December, between signature acceptance and signature application in Yousign Solution.
Yousign solution uses a cache system to store documents waiting to be processed, in order to serve the signature process in a more efficient way.
This cache has aliveness policy on each document, which aims to keep fresh cached files (older files are evicted for new ones). However, this mechanism provided aliveness of stored files for 10 minutes, linked also with a max capacity (both metrics enter into caching rolling policy), and in some specific scenario, this cache was simply unable to store in an efficient way files for a well suited period of time (peak usage scenario mainly).
During this kind of scenario, files were not served by this cache system, but downloaded from our external storage systems, and created a latency which proved to be significant enough to slowing down the whole signature systems in intense usage scenarios.
No signatures were lost during these incidents, the impact was only limited to delays in signature processing system.
Cache system was deeply reworked on 03 December by our Engineering team, we are now able to store more information into our cache system in a more efficient way which led us to speed up the signature process. We also created specific monitoring rules and collect more metrics regarding this system in order to prevent any issue on this particular mechanism. Our engineering team is also working on improving the signature system and a dedicated team is implementing new mechanisms to make even more reliable the whole signature infrastructure in order to avoid any related incident.