SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b333cd148bcf559d93086b4b3bafb377b63b2f6d23efd9a4421b679a5a035df5' 
  AND token = 'z2i8uTPLMXioltQutUjZxGV9dhhgNnOrsBm/orbkjvI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00072

JSON explain

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