SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f77704a79923378f1f9c29cc649941a9f333ade1bea253907502baed963c2f2' 
  AND token = 'PBYmWsYIPMzXSOgMurLClaz0tkeZ+c1O18ElwTAEF9Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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