SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '06856814ff0684761918f1012d152634e3f781b8189597aaa0e03eac16b0837b' 
  AND token = 'Mr+8TlJhZjSu+I15sOHuEcJ4KAlZz8iZSuQcMxYvnP4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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