SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e93f9d9af8e04c1716bac29fd365a70375518e922899233ade88e589c2b9a5f' 
  AND token = 'SegHoKbcs351xMOuYwBi4ErifG7pezSgPrbcRFRzEH0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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