SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3919d36fe21ba0cf5fabdbe1cb087320fb4e5568233342f95c3aa0acc7e3f22c' 
  AND token = 'uDrLsiDeRubXkph2vTctrz2aHBWRKayVzIcI4AKqsBs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}