SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6286feea54fe49d663533e92257dcdc953e3b35f25181d08b18a7ff439f9f819' 
  AND token = 'ftoH+qzVbHzNYKIXYjMukGUcwnL9kGQayyF7+1Gkv9w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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