SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8db63df61d7d66e594ce351bdb746f74860ea2000afc52eacf9b1f035791888' 
  AND token = '8rBfXJMrGgSRBq1CRiyZhq3/duWY96hpun6MrtPxO14=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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