SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '268498368a32596e172f27ab1c447b441f759e8358814e7d016807fe2d535f3c' 
  AND token = 'o0vMTgAwrfMLQxjDivdGhExMKpjFE0vNHWthTN8+DBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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