SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68eb08baaf764fe0bbee04742a22ac1aebf9027fd75abc8765cf18181cfda35c' 
  AND token = 'KUAE/VqDrW4egSxn3C4p3sZwTqoc6eq4AL7sQsGu+bY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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