SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15f120a07bc861b4939e966456045af847a78c881818479289f2385caa74819e' 
  AND token = 'oUP32HW9nNyItvzinXkKJik29wqvUUhmOOfuhO9wGP8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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