SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5642afb2e652856a1a84a27964734fdefb827db19228646a2032d97ad00315d5' 
  AND token = '5XH2wF9IRLfVkTGcSZFlKZ6PNlRq/WuRcBm5eyTVFkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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