SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6f65757b6de7f75de6f6134a1322f5d2caf18f924d553d6e47fd02e04631af4' 
  AND token = '6dIUFIYrGGjsFamVh3ovog3wsmMz+dxjg+RXN2bZFQc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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