SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5102e4349c02b7ab9c4d903992210b9092df89200cf5209cfacd3d0e4cf2d927' 
  AND token = 'z8CdQiZr8j7CbxG778XkovlDteJFzg576zSTtmpcDqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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