SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8236293d57608337986258120c01ede93c1f48bfafe71de9b6c998dbc989c756' 
  AND token = '216buwHVWgw4jSXQYTkk4cEkiZGj4yoBsKq7MSFiNpw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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