SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29af54b6a95bee0d3a22fe7769a42c15e195bc18dd411c5f295d4a687862f704' 
  AND token = 'USJxpa2hZwABsmin3fZfy8ejP+0Xz6uHz9VoV5ZQoSc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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