SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d5f08a3813b7df8f3b6591f1827e677720cae039c681de739f33319f91e4937' 
  AND token = 'gj/CcVF1eq6ylWFKHdvj+913LnWnDRwVYhhVYhm7IcY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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