A computer-implemented method for evaluating a performance of a system comprising a plurality of services provided by a plurality of computing systems, said method comprising: determining a plurality of call map clusters (210, 610), each call map cluster (210, 610) associated with a respective type of external call, two or more of a plurality of services, and a service call model modelling, for each of the two or more of the plurality of services, issuance of outgoing service calls in response to received service calls; deploying a bot mesh comprising a plurality of bots, each bot being proximate to a corresponding one of the plurality of services, each bot being configured to mimic communication characteristics of the corresponding service as defined by the models, said communication characteristics specifying one or more of: a sequence in which to issue particular outgoing calls, a processing delay between call reception and an outgoing call and a payload; and associating each deployed bot with a respective configuration to issue outgoing service calls in response to received service calls as modelled by the service call models for each of one or more services proximate to the deployed bot; said method further comprising: issuing a plurality of external calls for services to the bot mesh; in response to each external call, operating at least one of the deployed bots to issue one or more outgoing service calls to other bots in the bot mesh, based on its configuration, said other bots issuing in turn one or more outgoing calls to other bots in the mesh based on their respective configurations; monitoring the outgoing service calls; performing an evaluation of the system characteristics based on the monitored service calls, said system characteristics including at least one of: user respond time, required network bandwidth across data centers, infrastructure as-a-service costs. determining a plurality of call map clusters (210, 610), each call map cluster (210, 610) associated with a respective type of external call, two or more of a plurality of services, and a service call model modelling, for each of the two or more of the plurality of services, issuance of outgoing service calls in response to received service calls; deploying a bot mesh comprising a plurality of bots, each bot being proximate to a corresponding one of the plurality of services, each bot being configured to mimic communication characteristics of the corresponding service as defined by the models, said communication characteristics specifying one or more of: a sequence in which to issue particular outgoing calls, a processing delay between call reception and an outgoing call and a payload; and associating each deployed bot with a respective configuration to issue outgoing service calls in response to received service calls as modelled by the service call models for each of one or more services proximate to the deployed bot; said method further comprising: issuing a plurality of external calls for services to the bot mesh; in response to each external call, operating at least one of the deployed bots to issue one or more outgoing service calls to other bots in the bot mesh, based on its configuration, said other bots issuing in turn one or more outgoing calls to other bots in the mesh based on their respective configurations; monitoring the outgoing service calls; performing an evaluation of the system characteristics based on the monitored service calls, said system characteristics including at least one of: user respond time, required network bandwidth across data centers, infrastructure as-a-service costs. issuing a plurality of external calls for services to the bot mesh; in response to each external call, operating at least one of the deployed bots to issue one or more outgoing service calls to other bots in the bot mesh, based on its configuration, said other bots issuing in turn one or more outgoing calls to other bots in the mesh based on their respective configurations; monitoring the outgoing service calls; performing an evaluation of the system characteristics based on the monitored service calls, said system characteristics including at least one of: user respond time, required network bandwidth across data centers, infrastructure as-a-service costs.