SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f598149fa60e013ba41ec03bfd1969a897bfa0136805b6a67661b75a398fe546' 
  AND token = 'SDBx4l4Uhst0Fs8KK+vT/iUWL0d/AnZ5mWJz0u3HjEg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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