SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a790284273a71b31ad22d4010762811d34b3f9dd5576c845c48ca3260f12ace3' 
  AND token = 'fnPliMZozPIYS3uPnkfuwl6scPbhMWbPOI5zAyGdE1g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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