SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8f066b4fdb06f6212f88afa453a026545d4d96f8c145b5d9d0d9f9908cff517' 
  AND token = 'Q9eiZlml7Bhg+5TVKJOkC7UqgQWFhQ4qq5YHS0uq27g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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