async-storage-union-cache.js

import { AsyncStorage } from 'react-native';
import _ from 'lodash';

loadFromCache(model, limit = 0) {
    return new Promise((resolve, reject) => {
        _getModelFromAsyncStorage(model)
            .then(results => {
                if (!results) resolve([]);
                if (_.isArray(results) && limit > 0 && results.length > limit) {
                    results = results.slice(Math.max(results.length - limit, 1));
                };
                resolve(results);
            });
    });
};

insertIntoCache(model, record, { update = false, primaryKey = 'id' }) {
    return new Promise((resolve, reject) => {
        _getModelFromAsyncStorage(model)
            .then((data = []) => {
                try {
                    const source = update 
                        ? _.unionBy(record, data, primaryKey)
                        : _.isArray(record) 
                            ? record 
                            : [record];
                    this._setModelToAsyncStorage(model, source);
                    resolve(source);
                } catch(e) {
                    reject(e)
                };
            });
    });
}

clearCache() {
    return new Promise((resolve, reject) => {
        AsyncStorage.getAllKeys((error, keys) => {
            keys.map(k => AsyncStorage.removeItem(k));
            resolve(0);
        });
    })
}

_setModelToAsyncStorage(modelKey, values) {
    return new Promise((resolve, reject) => {
        AsyncStorage.setItem(modelKey, JSON.stringify(values), (error) => {
            if (error) reject(error);
            resolve(0);
        });
    });
}

_getModelFromAsyncStorage(modelKey) {
    return new Promise((resolve, reject) => {
        AsyncStorage.getItem(modelKey, (error, result) => {
            try {
                if (error) reject(error);
                resolve(JSON.parse(result))
            } catch (e) {
                reject(e);
            };
        });
    });
}

Загрузка
this.loadFromCache('todos').then(todos => { ... })