SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8b7c4bc0fd35174054557364488e4173b1b8fcd41bcf42c7d907f3f11062c82' 
  AND token = 'rDXapdQoLVAbTKGBD50mmYFq4AsQww4e+vpaHUwZH8s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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