SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8621ab41d2217f008b0d6cc87d4a1bde7772d6c369d5603364ead76d508705d' 
  AND token = 'hC9uHmBKw1BnPpdbOK7BaReBZ32WNdEVmG85q6BQguA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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