SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd5833b777c1257ea1d8376621b2a31a169d88f0d41b9036e8b131ad2adf22a40' 
  AND token = 'l3RGzwDSPEtXJl5MYiPYJZnW0VLP6Wqow0zGggQ4RRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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