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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b39b9f0685492e443ed3b1e831b3667d3c4a887b4842f7351e8a240cc1b43b8f' 
  AND token = '+3ayFYw3TMIs7Wjj0jSr9AV5+ljr01QtNmjaKv10Ze0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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