SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6812261cf431bcb3c4ff221f9a057d174b39e3d28660c97da2d8346828ceeb4' 
  AND token = 'ijysdMhfLrM9EfMzgdefsjHtt69Elw8CfYselSEgME4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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