SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1e94df21b48402a32197379d48d256fd8552171b87ea444816830a5071183c5' 
  AND token = 'yWnJ2/ZejG8i9afnN7Lw8VzYzNOU9UjjSiw5OslCoLU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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