As a relatively new concept, data lake has neither a standard definition nor an acknowledged architecture. Thus, we study the existing work and propose a complete definition and a generic and extensible architecture of data lake. What’s more, we introduce three future research axes in connection with our health-care Information Technology (IT) activities. They are related to (i) metadata management that consists of intra- and inter-metadata, (ii) a unified ecosystem for companies’ data warehouses and data lakes and (iii) data lake governance.