SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5d561b2bd84aa978d082807664cd9cac7e3840b661207ccc62c0656d6215c450' 
  AND token = '6uk65oEM4bKE/jAExihNXybdccUn8LiulzAIzqBwXcI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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