SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '840d3a0a581e8fe775a97f5b27fe4049c7353363715271986d19722b95605779' 
  AND token = '3naeLJrmlj6Y+usat6ehRzI/E8wDAYrQTfZhoz+6BA4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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