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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a99c2f8d69f68ed620662db8dc1b57f2e4d25aee2a1e832bc9cac4ad4876b790' 
  AND token = 'MXY4yQpiqFpUrQ8sDBf99IYYV67mjuu+kdZIusyPUpg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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