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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '30f7753e61ffe1e9e7e442d1f24d71a65ddf1f4b4f3a70eed7f0ab9db95aba37' 
  AND token = '75B0kz7juDO+mqIGrDyc7ZFdeZ1cP2pSO88FMNpZE9E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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