SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b9d51540ea8d02a2f5016c4da3c532577ff67a9f57da22b51964ad69162a4f0' 
  AND token = 'YlhwPBIK2qkFjKuDhyj+RxzAyTl591cRRxLJ9zNFJig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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