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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '31d5d9e07482471a25a8784d1cec398ca1dbe153b79eb8f0c7c9a06fcb8106bd' 
  AND token = 'eBkhJ1Tn1qh6tnMFJgsjEA8vrPk10MLy9FEthbxKFXU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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