SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8b6d77eef5ca4106b25ad09e523986cc819dd3f9f817e27c33ed6fc1417b47c' 
  AND token = 'p1wZ3vEjVpVynBYq+/niYsHEiVWQKMlFSfUFwUbI2eY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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