SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ce2a7f1ce88ff8bf75b0fa4204333b4894b6252a0460db519d241117c9d5e424' 
  AND token = 'gnfsIYS975S51g84t1XiTs2rEy+PVPe7fJ6/uHodR1c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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