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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'af6a30f85565c07c3b101031a9b377d835685b8a93680a1c901d15b8fce9d9b6' 
  AND token = 'z/eRKiIhhPofFAJsFxXnO+CaP8cI3cbUMpIPN1kE6r0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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