SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '828a2897e7abf673ceba10c0bca936084466a3007f23d591281de0c73ac59374' 
  AND token = 'iiFttebKRoMsfeKBupVqVcvYDhG9dndd7KQdD5RAv3w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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