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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6957a340a46e1bece2053874a2ecf77be17d4eaaf70c090baa77502f4dfbd2d' 
  AND token = 'Xr7ls+kMzQiFd4fNr3Pe7KlPvIRYbY0VhObBPnQW7hA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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