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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7821839617c4f7f9bf7e57527fd506873d865530dafb61747e87d63abc4cae54' 
  AND token = '56a659B3UNpvfiXiET5mWg1H7G+1hoVin/38yh9yPW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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