SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51dd7a15e812b9d6756520f1773c8d7c00c101dd583bba1dc22e7f01833cf75' 
  AND token = 'Kd35MadGYGNq/IYrNyT+C4mqaVSlSWa62d3aWGsHcOE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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