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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8b3fdf4ec501bb3eb11f07c5847a0d805f51ed15f1d1dbde0e556d594c8adf2' 
  AND token = 'e3FJcpt2BBUdEmeFkEPM0jNZUOCbUpnWqo5Rpcm+spM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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