SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a81b05c87da6df84b46723b3a2c652b068983732156623a69685889eb3f08fbf' 
  AND token = '2+a5bpPq1+YKwYe1KVDMqMh4KT4TGyg0/vOHXHcuDOM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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