SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83702ac93736bb44b6f0063da73baf865f20d651dba9594e916859ea5f7441fa' 
  AND token = 'LXiNg/zFth4V4T1NHcTt4p3qUsUUmlPCPtNYtVRcGVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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