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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2734c0f37026887d2754a94b41119cd764b71310008e2725c955ec6039b696c1' 
  AND token = '6+4lJJ2k+BatynTra8+j5ePDFNtC18TcVuVWLDHiex8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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