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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '431c3f10edfcd182385adebe3136be6693e61536e6fc711e68b7d28d47e9c1e9' 
  AND token = 'I+A+JVS3hxwal/AnAAvWS7CfOVCMbNmtGhcDcVVI7lM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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