SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fb9a2a064c6880fd82d815f0cf914bd2e5f54a88456b998bc573d7214ccb588' 
  AND token = 'cH7qOkNvDgGkCMdmpm75lH7AWC2YzsNNuJwnrbKjcXE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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