SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '818d9481d6423b782b8a08eedf825b46974942d430ae737756938a3aa7b5a4fa' 
  AND token = '5JLXSQPAmrdLL7M/uu+BHvItv7IUoErISEGtvaYAaF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00078

JSON explain

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