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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '100cb31fc8c56f15933b693c7344a66376082f1ad12b7f7f9363d527d8376f43' 
  AND token = 'BKYtjcJYr5TZMx2YttjntdTsy8nIEx2qSPQfN0xzJ7M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}