  Blockchain technology is affected by massive limitations in scalability with
consequent repercussions on performance. This discussion aims at analyzing the
state of the art of current available Layer II solutions to overcome these
limitations, both focusing on theoretical and practical aspects and
highlighting the main differences among the examined frameworks. The structure
of the work is based on three major sections. In particular, the first one is
an introductory part about the technology, the scalability issue and Layer II
as a solution. The second section represents the core of the discussion and
consists of three different subsections, each with a detailed examination of
the respective solution (Lightning Network, Plasma, Rollups); the analysis of
each solution is based on how it affects five key aspects of blockchain
technology and Layer II: scalability, security, decentralization, privacy, fees
and micropayments (the last two are analyzed together given their high
correlation). Finally, the third section includes a tabular summary, followed
by a detailed description of a use-case specifically thought for a practical
evaluation of the presented frameworks. The results of the work met
expectations: all solutions effectively contribute to increasing scalability. A
crucial clarification is that none of the three dominates the others in all
possible fields of application, and the consequences in adopting each, are
different. Therefore, the choice depends on the application context, and a
trade-off must be found between the aspects previously mentioned.
