SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f1e87084508fd138f607b240957de2c51be3662124903f349e3cdbde7cbc324' 
  AND token = 'dxSYgUi/I3STwhUKSUKgEBw8iQ/+20EhnHsVz1Mx/MY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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