SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '92a7e8993dfc4622e12316f659e5b7f17d864077fbe3f2adfb587c98ebf138e4' 
  AND token = '4uxvEuwpTCYhlxEo+q6ZmQ9eLNWJjg2P7HYryU2Q+zA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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