SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f63c1a218872987d9ac2c26062cc9b97c4e3d2ef9586db7458dcd60b1a670e' 
  AND token = 'KNqmjIUSU5TVUhAgpf44+4So5/KseBAmawJKjgArTDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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