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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a42c7f3b21643d3735a2a549cc225792229f3646fd929f05ab4e64d5cc639b20' 
  AND token = '5z/d41jD8Mmc363mAcTzHvVlFqKckiKPkCtPOfh4y2Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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