SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9476b7af338f5e3286182c2398f091c512e19615f657c6d0426c594cde5d68d7' 
  AND token = '/hKutikHruRJweOHQjlNi0FUlroLLwPVxcZBjo8eFmo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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