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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '557b9cc0b055d76d716182478a055b623de502f571cc8db2dae90615ee3e45b3' 
  AND token = 'UIaDh76i6XY8/bEp4eOowVuCFGcshdGGcWXmDqt6UxI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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