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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '51f2ad3a6fda7de048fd3366c8e4c2a7fd8273968f0c0965176c617684b9f5e7' 
  AND token = 'sLDj2x2tMcqySAbNTj8gZkPdyjBp/WzLygATFux74sA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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