SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c299bdd8cbf5c10854c820feee0f5bb9b0214e35daf52d5141698e49d3a5c684' 
  AND token = 'RfBwHjI2pOWAiikQvJnnr0MS9MVuNelbznfwwl8ySyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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