SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68c53064140be92d1b207678c803e3f53dfabaf0cffb690aadda0f0977e76ab7' 
  AND token = 'I/KJQ/khHtEhiA8XBviNnUGLdVm/31wR4bqaomOUXDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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