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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9e1df5aa0f25fe7a2958e9a9af0ee085a795313e8afbd0b7d0bb03356f74f7b' 
  AND token = 'BcwHtXn206/88A6UaTExU8u2ioH2CrUbBSyHTzdUN9k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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