SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b78ff017acbc7aaf0d6eb92b4eb0e972f112028b4f35dff61ecd82fa9285aa8' 
  AND token = 'DJ66aJA4BU/VALEGM7hUQwhpkw+pSczZimuot9wsLZ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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