SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e51173a3c74176115689e49534f94e30614ef10da931fec189652b6612b6368' 
  AND token = 'asCs2liKMVklRp9L4ljEx7wDO8sQfbzcDCAtf6pQ7V0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}