SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd324284fe29dbc9b40902841894d28507d88c7a2c204300bd9e7bdbded7a9958' 
  AND token = 'pOUEwdGmVPxTPprDZwyYRs62mz0hLmEjgW1xMiBujjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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