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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9aa6f71994b47192de6513e9398b352ee97effd5f15150a66d1d0abc1077a4c' 
  AND token = 'uB0S4Jr9YAoP6+dTC/PTg/Nhihm4WaW/UuKtKKE7qmY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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