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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '21fdb8187d9155c16542dda1297477b3c941b5ff53967e8f15d02937616ec1ed' 
  AND token = 'bI8dbquAePxPjfbDDS1Mk1eeljEVX24zZ3/UvmLHnlc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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