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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f5b48bc835e3b7d90e137bf40bde0cc6fa1975cea6e0a8a00b94cf29b4dc1178' 
  AND token = 'kZ9RD9C/MNXO4vrvow7mbMqsGPzdPEqoIUZ+g48egVc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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