Russia having to ration artillery shells

 ISW:

...

Russian forces are likely depleting their stocks of artillery ammunition and will struggle to support their current pace of operations in certain sectors of the frontline in Ukraine as a result. Ukrainian Main Military Intelligence Directorate (GUR) Chief Kyrylo Budanov reported on December 31 that Russian forces in Ukraine are experiencing significant issues with artillery ammunition that will become more pronounced by March of 2023.[8] Budanov stated that Russian forces had previously used 60,000 artillery shells per day (as of some unspecified date) and now only use 19,000 to 20,000 shells.[9] Budanov stated that Russian forces have also removed all remaining artillery ammunition from Belarusian military warehouses to support their operations in Ukraine.[10] The United Kingdom Ministry of Defense (UK MoD) reported on December 24 that Russian forces currently lack the necessary stockpile of artillery munitions to support large-scale offensive operations and that sustaining defensive operations along the lengthy frontline in Ukraine requires the Russian military to expend a significant number of shells and rockets daily.[11] ISW assesses the constraints on munitions will likely in part prevent Russian forces from maintaining a high pace of operations in the Bakhmut area in the near term.[12] The depletion of the Russian military’s artillery ammunition stocks will likely impact their ability to conduct a high pace of operations elsewhere in Ukraine as well. This Ukrainian report that the Russians have already depleted ammunition stockpiles in Belarus is a further indicator that a renewed large-scale Russian offensive from Belarus in the coming months is unlikely.

Russian forces launched another round of missile strikes targeting Ukrainian critical infrastructure on December 31, but this round was of reduced intensity compared to previous rounds.[13] Official Ukrainian sources stated that Russian forces launched over 20 air-launched cruise missiles (of which Ukrainian air defenses reportedly shot down 12) and used 10 Shahed-136 drones and an Orlan-10 surveillance drone (all of which Ukrainian forces reportedly downed).[14] ISW cannot assess at this time whether the decreased intensity of this barrage resulted from Russian missile shortages or whether Russia can continue to conduct intense waves of strikes. Russian milbloggers continued to describe the scope of the attack using similar reporting and reactions as they used for previous rounds of missile strikes despite the reduced intensity and impact.[15]
...

Earlier reports indicated that Russia was having to buy artillery shells from North Korea.  If that is the case the Norks may not be able to deliver all Russia needs to sustain its war effort.  If Russia is also still using Iranian drones it is because it is likely running low on its own investor of rockets.  

Putin continues to be unrealistic about his war with Ukraine.  He grossly underestimated Ukraine's resistance and the support Ukraine is getting from the US and its allies.  He also overestimated the effectiveness of his own forces.