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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a8ef40dc3c44445f89cbf35f1793fe1dfbf6e73fe01a3d96c8ceeb2843490c4' 
  AND token = 'f/v9BRISO9r49ya9ZEUqv0D/e0GoXqtsnUfsIzMMVF4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}