SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6bcab20807c8674de219e4f61a3bc0b37843d3679a951fd2422c55b7dbde1ac' 
  AND token = 'JED+y75Pw+Q5Zjw/1WVMFx4IE6Vq+OOvieVxhfzfsvA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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