SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '835796b9db623d1773fcb80142f0c5d3c938f5e3e4f3c5a29975d44db239dd53' 
  AND token = 'kt9VqSrnDq8c1OATHN8EBNKrOhyCFZJdkoeuPpk38uM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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