The simplest and most suitable solution that meets the latency, security, cost-effectiveness, compliance, and scalability requirements involves using services that ensure fast data retrieval and a managed model deployment. Cloud Bigtable is recommended for its high-throughput, low-latency capabilities, making it ideal for real-time context retrieval. App Engine serves as a scalable gateway, and AI Platform Prediction simplifies model deployment. This combination effectively addresses the need for performance, scalability, and simplicity. Option A is also considered for scenarios where the simplicity of deployment is prioritized, but it may not fully meet all the scalability and data retrieval speed requirements as effectively as option C.