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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ec78c69aa9239e95993950bfeae2b3dc499c6e5c03796403bea01c6ad926051a' 
  AND token = 'MQMq96hNG4xUjettiyRq7WSWD/HoDS3NLl2wi9a23oQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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