SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4209b176a7b20f3c47ecf5380bc9c0eff862529d8654970e48cb4efd98da1def' 
  AND token = 'FNVXRPGXMg+EfEQi7fhwZG+a182lvqKm5DrxWV5npe4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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