SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f750d19611e2b41b5f77babddee5ccb4ee254af68feb941c79d38314f46a4f2' 
  AND token = 'zMr0hBHjfjGkSYteYonW+4Qi+QnomtEadqL3wewEZcI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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