SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8a21701a80170babd78949e885cb7a319df59af550e40196253ba059f0f7033' 
  AND token = 'LKy8aDgiagcS0wrRCmfIPTBt26tPkwZ9Lde4OyCsvgY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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