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Second hand selling application using several gateways

Case Study - Letgo

Letgo is the biggest and fastest-growing app for buying and selling locally.

Letgo is both a desktop application (SPA) and a mobile application with native implementations for every OS. As Letgo’s organization is large, the UI experience of each client is handled by a different team.

Letgo uses different clusters of KrakenD API Gateway per client, allowing each team to have its customized views of merged data. The API contract used in every device is preserved and respected even when the backends need to change their specification. KrakenD provides automatic aggregation and filtering capabilities that provide to the client a simple API for each device and team needs.

Letgo makes intensive usage of all authorization and token revoking features allowing legitimate end-users to be accepted and illegitimate users discarded at the API layer without impacting any backend. KrakenD API gateway inspects the JWT tokens and makes sure that every user is inside the allowed usage limits, with a valid signature and possess enough permissions to view the requested endpoint.

Letgo also uses KrakenD’s bloomfilter, which are ideal for supporting a massive rejection of tokens with very little memory consumption when needed. For instance, 100 million tokens of any size consume around 0.5GB RAM (with a rate of false positives of 1 in 999,925,224 tokens), and lookups complete in constant time. These numbers would be impossible to get with a system backed with a relational database and allow Letgo a quick response on a distributed, stateless, and decentralized system.

About Letgo

Letgo helps make secondhand second nature by making it quicker, simpler, and more fun - and with over 100 million downloads and hundreds of millions of listings.

Visit Letgo

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