SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4cdb7e64276ea02086e84ef1332979ddf84998e62933dea84371298a460fd04' 
  AND token = 'FQbQiInv6PZOoygzpyvIMBHEpXRI1AqQjPKFQy0rFTE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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