SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d91d023677231f6634100d1da10763abd45bef7da1744a17f061f65c892564d' 
  AND token = 'H2CYib7s7KMWJl0klGV6wUiAsmvO5DIa7+LdE8WoSgs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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