SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42fb746807f9a282c684cceee65a49592d62bc61e08c593b5cb31f9a10fe6162' 
  AND token = '78JReQhR9/FqrqxhIjxIfKIPgPcefrZ2LxXwzd0ovM8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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