SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b9dbc8ef1340c3ff7b67137985affabda68ec8a3b57717f2391338a4072bb3b' 
  AND token = 'Y+hBCWlgqxwHBbXQY2B7MYHQLmA1bIbKaJzKksm8eCs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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