SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0a6f8ed344767b815e1b218bfd28d3414a0d36bf7e4fbc4a67ff80a0a7c644ed' 
  AND token = 'V++bjfYot3EJOd3C48gSlc624GSlbiLbSjkD8sEIRwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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