SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4e237f5812ff641c78739f53477f76b69b68d8be5daa5063b2cbfac2fe6a656' 
  AND token = 'MlTf9qkzRnjLYTZNpYgF7T5CH7vb7CBvgTaGwMywObU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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