SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a2d55308153e0e14278dba2112a95525ab51929c80eb0119921786793cd9aa' 
  AND token = 'KyG5ALuxPlNY2MQGhQjJzZbVzUt7WKqfHyuZPkT2B4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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