SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b8ea7fef8d8280d824c41d630edb87d4045a23b36f31c64d1495f1d28ef69b3' 
  AND token = '+owH6XPcvHnlnEt5UyazASrhYvn1uZAhhfMZGCw7NmY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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