SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6086b18e2003c02640d50d667450920c6b9a40abf21e55a5ee2c83017191189' 
  AND token = 'Kp+46E8529TFfy++moscE0zXUawmWpHDymRwXzfhKdM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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