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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83ad210b52df15ce5d7f73949a1c2bb50aba874f0a70b2436b4a2fa72378fe96' 
  AND token = 'NxxeHshg9b+NdfPIzwo+HmMvTzEcjv+EOzWQBTg5DFk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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