1. A computer implemented method for assuring performance of an application across various stages of development life cycle of the application, the method comprising: obtaining, by a processor, at least one performance requirement associated with the application in a pre-development phase of the development lifecycle of the application, wherein the at least one performance requirement is indicative of qualitative performance of the application, the at least one performance requirement comprises at least one of operational load characteristics associated with the application, key transaction characteristics associated with the application, batch job characteristics associated with the application, expected service period of the application, expected availability of the application for operation, acceptable utilization of system resources by the application during operation, and data retention period for the application; mapping, by the processor, the performance requirement with one or more functional requirements associated with the application to link the performance requirement with the one or more functional requirements, the mapping being achieved in the pre-development phase of the development lifecycle of the application, the pre-development phase being before a design phase and a construction phase, wherein the mapping comprises, creating a list of use cases for the application; selecting a set of primary use cases from the list of use cases for mapping the performance requirement with the one or more functional requirement; analyzing, by the processor, the performance requirement against at least an operational load expected to be handled by the application during operation; developing, by the processor, the application based on the performance requirement, the mapping, and the analyzing; determining, by the processor, a plurality of performance characteristics associated with the application in response to testing of the application to compare against desired performance characteristics for assuring performance of the application during operation, the desired performance characteristics being based on the performance requirement and the one or more functional requirement, wherein the plurality of performance characteristics are indicative of quantitative performance of the application, the plurality of performance characteristics comprising response times for transactions carried out by the application, response times for database queries, number of transactions completed per second for batch jobs, throughput of a system hosting and running the application, utilization of system resources and input and output resources by the application, number of application instances executing concurrently, and number of physical servers hosting the application at various instances during testing; processing, by the processor, based on the comparison, the plurality of performance characteristics to obtain performance characteristics of the application for varying performance requirements in a pre-deployment stage, wherein the processing comprises generating a deployment matrix for the application to indicate the plurality of performance characteristics of the application for varying performance requirements, the plurality of performance characteristics being determined for varying performance requirements by extrapolating the plurality of performance characteristics; and deploying the application in a production environment in response to the processing.