SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '708db19c52828a5248e50a2309a4c640bba1bc9eeef3e0b643b077193582c42d' 
  AND token = 'OQLC1kk01PeL3zofRm7NxtHSIhp4HIqWMAA4KPjj7TU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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