SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2f8add7438285cfa8af8e995b428660e9a57ec0763c4d91a3361ba005b3e6043' 
  AND token = '7x6qrW+DmL3uHhAE7BeFMSvCcxnZHIdhwtVVYsXGeK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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