SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b91f4d75ace9cb87ee327289157f2f3ad5d4850cd060fc18f1a28638b88239c' 
  AND token = 'nEwXJuGcvq+Jel+TyTKHUB6jshfnTvAJojOmyDq4dYA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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