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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '717e8671b64c0b8d72e6df39e4f105c542d9f57aabde28a24c722f5a96a19648' 
  AND token = '5AFvoYWPVL+VccvBnHDW3xx8ieIxdi74niKEKgf2CDI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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