SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12e1b9ccb05210449285d67991dc91534c6b2d3c607ad1847761002770ba63de' 
  AND token = 'RFxoQdpRd7XCyuQBljsaLDFjEQch8j7gr735+BdP7fQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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