SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b207426603e5659b8257ec2dff713f82840c8dc1f4d798621d4777b1aa046a04' 
  AND token = '1yUSfttWfdy1IutKYTNTIy6s6JqEPQwkS30EGkKNEDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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