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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a3ae75fc34f270a70fcb6bab546df9c7dbfd3154fecb7abadb31483051a9a90' 
  AND token = 'xCB3z9F1WQAj9sovmtnuGt5norcenHilo/mf0RpUMU4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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