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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '509e4dedf3a61cdabc24d054d1ea25f1b27e5e7f0f0463d558ffb6f2686d52d6' 
  AND token = 'ipZcaKVG+bzcMLZddLvt/SY+rdLi9VlElgfUZ2crhDI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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