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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a12dba99a508b85c0435d0696eaca1ae2d6e87f58cc53c2a9e1ed0a43308ff2c' 
  AND token = 'NlC89b4vGJOfPppY29ohfHacY17dNuAs1ZOncDVc8Oo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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