SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '275f7d6cbc4d73f8f3b38479b459f84c538bda4b01667a79d91ade785d21b19c' 
  AND token = 'xmqptVS1+0/0CSWgpnaYL49wqj3eLAVku5uDf+qLrRI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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